DUBAI, TEHRAN - Iran has pursued a longstanding effort to buy banned components for its nuclear and missile programmes in recent months, a US official said on Sunday, a period when it struck an interim deal with major powers to limit its disputed atomic activity.Vann Van Diepen, Principal Deputy Assistant Secretary of State for International Security and Non-Proliferation, said Iran was still "very actively" creating front companies and engaging in other activity to conceal procurements.The reported supplies do not contravene last year's breakthrough agreement between Tehran and six world powers to curb its most sensitive atomic activity in exchange for some limited easing of sanctions damaging its economy. But such trade would breach a 2006 UN embargo banning the provision by any nation to Iran of materials related to its nuclear and missile development work. Western experts say such low-profile procurement efforts by Iran date back many years, perhaps decades in the case of its nuclear activity.Asked if he had seen a change in Iranian procurement behaviour in the past six to 12 months, a period that has seen a cautious thaw in US-Iranian relations after decades of hostility, Van Diepen replied: "The short answer is no. "They still continue very actively trying to procure items for their nuclear programme and missile programme and other programmes," he told Reuters in an interview."We continue to see them very actively setting up and operating through front companies, falsifying documentation, engaging in multiple levels of trans-shipment ... to put more apparent distance between where the item originally came from and where it is ultimately going." Asked for reaction to the allegation, a senior Iranian official replied: "No comment". Van Diepen did not say what sort of components Iran had sought to obtain or which part of a government known for having competing hardline and moderate factions was responsible. In the past, Western officials said Iran's elite Revolutionary Guards and the Defence Ministry - both hotbeds of opposition to any rapprochement with the West - were believed to control clandestine nuclear procurement efforts.Those talks got under way in Vienna last month and a second round at the political director level will be held on March 18-19, also in the Austrian capital. The aim is to reach an agreement by late July, although that deadline can be extended by another half year if both sides agree. Iran has one of the biggest missile programmes in the Middle East, regarding such weapons as an important deterrent and retaliatory force against US and other adversaries - primarily Gulf Arabs - in the region in the event of war.Its efforts to develop, test and field ballistic missiles, and build a space launch capability, have helped drive billions of dollars of US ballistic missile defence expenditure, and contributed to Israel's threats of possible pre-emptive military action against Iranian nuclear installations. Since Iran is not a self-sufficient manufacturer of missiles, the expansion of its inventory depends on the import of goods and materiel sourced abroad. Van Diepen said that while there was no direct link between the level of Iranian illicit procurement and the negotiations on a settlement to the nuclear dispute, "obviously if the negotiations succeed then there should therefore be a corresponding decrease in Iranian proliferation activity."Foreign Minister Mohammad Javad Zarif said on Sunday talks with world powers this week are unlikely to result in a comprehensive accord on Iran's controversial nuclear drive. "This round of talks will be more serious than previous ones," Zarif said in remarks reported by the official Irna news agency."But we do not expect an agreement (in this round), as it is not expected in the timetable we have agreed," he added. Iranian negotiators and representatives of the so-called P5+1 group of world powers resume talks in Vienna on Tuesday for the second time since November, seeking to transform an interim deal into a long-lasting agreement by July 20. According to Iranian media, the latest talks will wrap up on Wednesday, a day before Iran celebrates the Persian New Year. Under November's interim deal, Tehran froze certain nuclear activities for six months in exchange for relief from punishing sanctions hitting its economy. Sensitive issues must be resolved before a comprehensive agreement can be struck, a deal that would allay Western suspicions that Iran's nuclear programme masks a military objective, despite repeated denials. These include the scope of Iran's enrichment programme and Western demands that its bunkered Fordo uranium enrichment site be closed, along with the Arak heavy-water reactor.The unfinished Arak site, which Iran says will be used for research, could theoretically provide Tehran with an alternative route to an atom bomb. In Tehran, more than half of Iran's 290-member parliament issued a statement on Sunday warning against "any restrictions on research-related activities", particularly Arak and uranium enrichment. They also said Iran's "defence issues, including the missile programme" - which could provide Tehran with a device to deliver a nuclear warhead - should not be discussed in negotiations with the P5+1.The group - the United States, Britain, France, China and Russia plus Germany - is seeking to pressure Iran over its ballistic missile programme as part of a comprehensive deal. Final decisions on key affairs of state, including Iran's nuclear drive and its missile programme, rest with the ultimate authority, supreme leader Ayatollah Ali Khamenei. An official in Khamenei's office and former parliament speaker, Ali Akbar Nateq Nouri, said at the weekend Khamenei was kept appraised of "minute details of the negotiations" by the foreign ministry, the Jomhuri Eslami daily reported. Khamenei is sceptical about a lasting deal. He said in February that the talks would "go nowhere", but that he was not against trying to reach an agreement.AFP/ReutersSIMFEROPOL, UkraineCrimeans voted Sunday in a referendum to join Russia as tensions escalated in eastern Ukraine in the worst East-West crisis since the Cold War.Russia President Vladimir Putin vowed to "respect" the outcome of the vote in a region that is now under the de facto control of Russian forces despite an international outcry. Russian flags were being flown everywhere from city buses to convoys of bikers roaming the streets as thousands of people went to the polls in the strategic Black Sea peninsula. "This is a historic moment," Sergiy Aksyonov, the local pro-Moscow prime minister, told reporters after casting his ballot in the regional capital Simferopol.Cossacks and pro-Moscow militias were patrolling outside polling stations and Russian troops guarded the unofficial border between Crimea and the rest of Ukraine but the atmosphere was largely celebratory.Ukraine's defence minister said Sunday his forces in Crimea had reached a temporary truce with Russia aimed at easing tensions surrounding the Black Sea peninsula's high-stakes secession referendum.Russian troops seized the Ukrainian region at the start of the month with the help of pro-Kremlin militias in response of last month's fall in Kiev of a Moscow-backed regime."Agreements have already been reached between our commanders... on there being no attempts to blockade our military installations until March 21," Interfax news agency quoted Tenyukh as saying. "We have reached this truce, and I think it will remain in place until March 21."However in the flashpoint eastern Ukrainian city of Donetsk, pro-Russian groups in favour of holding a similar referendum stormed the local headquarters of Ukraine's SBU security services and the prosecutor's office demanding the release of their self-appointed "governor," an AFP reporter said.Ukraine's new government and most of the international community except Russia have said they will not recognise a result expected to be overwhelmingly in favour of Crimea's immediate secession.Putin told German Chancellor Angela Merkel he would "respect the choice of Crimea's residents" and accused Ukrainian authorities of fanning tensions in mostly Russian-speaking eastern Ukraine.Ukraine's interim President Oleksandr Turchynov, who last month replaced the ousted Viktor Yanukovych, in turn accused Russia of fanning tensions in eastern Ukraine as a way of justifying an invasion."The result has been pre-planned by the Kremlin as a formal justification to send in its troops and start a war that will destroy people's lives and the economic prospects for Crimea," he said.There were signs of a possible easing in Crimea as Ukraine's defence ministry said its forces on the peninsula had reached a temporary truce with Russia to lift the blockade around Ukrainian bases. But there was no sign of the agreement being implemented at the Perevalnoye base outside Simferopol, where AFP reports saw Russian forces still in place.Tensions remained high in other parts of Ukraine's southeast, where three activists have been killed in the cities of Donetsk and Kharkiv in recent days. Around 1,000 pro-Moscow activists rallied in Donetsk on Sunday to support Crimea's referendum and 2,000 turned out in Kharkiv with a large Russian flag and a sign reading "Our Homeland is the USSR".Crimea is inhabited mostly by ethnic Russians and has been seized by Russian forces after last month's ouster of Ukraine's pro-Kremlin leader in February, sparking a security crisis on Europe's eastern border. Some Crimeans who requested anonymity said they would spoil their ballots in protest and there was a call on social media for people to cook vareniki - Ukrainian dumplings - instead of going out to vote.Crimean authorities denied irregularities but accredited journalists including AFP were prevented from entering some polling stations in the port city of Sevastopol and Simferopol, and several people were seen voting even before the polls had opened.Foreign observers were present although the Organisation for Security and Cooperation in Europe (OSCE) said it would not monitor because it was not officially invited by Ukraine's national government.Crimea's indigenous Muslim Tatar community, which was deported to Central Asia in Soviet times, largely boycotted the referendum. "Of course we are not going to vote," said Dilyara Seitvelieva, a community leader in Bakhchysaray, an historic Tatar town. "The situation is very dangerous," she told AFP.Mostly ethnic Russians were seen casting their votes at a polling station in Bakhchysaray. "We have waited years for this moment," said 71-year-old Ivan Konstantinovich. "Everyone will vote for Russia," he said.Voters can choose to become part of Russia or retain more autonomy but stay in Ukraine - a vote for the status quo is not an option. Out of dozens of people polled by AFP, none said they were planning to vote for the second option.Preliminary results were expected to be announced soon after polls close at 8 pm (1800 GMT). The referendum committee said turnout was at 64 percent two-thirds of the way through voting.Rehearsals for planned celebrations have included the slogan "We are in Russia!" beamed on to the government building in Simferopol, leaving no doubt about the expected outcome.In Sevastopol, home of Russia's Black Sea Fleet since the 18th century, the mood was celebratory and patriotic Russian military songs blared.Preparations to become part of Russia - a process that could take months - are to begin this week if the referendum result is pro-Moscow.Russian troops and pro-Kremlin militias took control of the strategic peninsula soon after Yanukovych fled Ukraine for Russia in the wake of three months of deadly protests in Kiev.There has been no armed confrontation between Russian and Ukrainian forces but several incidents involving journalists and pro-unity activists condemned by Amnesty International as "extremely worrying".While the West has been powerless to stop Crimea's annexation, Russia faces a painful round of sanctions against top officials that Washington and EU nations are set to unveil on Monday and it could be ostracised or even ejected from the Group of Eight (G8) leading world powers.Local authorities are calling this a "Crimean Spring" but many Crimeans are concerned about a possible legal vacuum and economic turmoil.One immediate worry is about the availability of cash and there have been long queues outside banks with Crimeans rushing to withdraw their money.Crimea would not automatically join Russia after the vote and Ukraine's government has said it cannot survive since it depends on electricity, energy and water supplies from the mainland. In Bakhchysaray, Anna Ivanovna, 70, said she had voted to join Moscow, but was apprehensive. "Yes, we will be Russians. It's good but at the same time, at my age, it's hard to change countries," she said.Meanwhile, Ukrainian Prime Minister Arseny Yatseniuk vowed on Sunday to track down and bring to justice all those promoting separatism in its Russian-controlled region of Crimea "under the cover of Russian troops"."I want to say above all ... to the Ukrainian people: Let there be no doubt, the Ukrainian state will find all those ringleaders of separatism and division who now, under the cover of Russian troops, are trying to destroy Ukrainian independence," he told a cabinet meeting as the region voted in a referendum on becoming a part of Russia.Meanwhile, China abstained from voting on a United Nations Security Council resolution to condemn the referendum in Crimea because it does not agree to a confrontational move, its foreign ministry said Sunday.The referendum underway Sunday in Crimea - to decide whether it should rejoin Russia or stay with Ukraine but with greater autonomy - was denounced in the Western-backed UN resolution as invalid.The draft resolution received 13 votes from the 15-member council at an emergency vote Saturday, but was rejected after permanent member Russia exercised its veto. China, which often backs Moscow at the council, chose to abstain."China does not agree to a move of confrontation," foreign ministry spokesman Qin Gang was quoted by state news agency Xinhua as saying Sunday."We call on all sides to remain calm and exercise restraint to avoid further escalation of the tensions," he said.