LISBON - Iran’s foreign minister said Wednesday that US President Barack Obama was ‘responsible’ for making sure that Washington respects a final agreement over Iran’s nuclear programme even though Congress has been given a say on the accord’s fate.

“It is the obligation of the government of the United States to implement its international agreements. And we will hold the US government, the US president accountable” for the application of the treaties that they sign, Mohammad Javad Zarif told journalists in Lisbon.

He was reacting to a move by the US Senate foreign relations committee on Tuesday giving the green light to a bill that would give Congress the right to review a possible final agreement on the Iranian nuclear issue.

Zarif, Iran’s chief nuclear negotiator, said Iran would study the bill “to see if it infringes upon or hinders the capability of the president to carry out the obligations that he is going to assume with Iran.”

Iran wants sanctions lifted immediately the deal is signed, while the powers are saying they will be eased gradually, and want a mechanism to ensure they can be swiftly re-imposed if Iran breaks its word.

Zarif also said that Russia’s decision to go ahead with the sale of S-300 air defence missile systems to Iran is “fully legal” and has no impact on the talks for a nuclear deal with major powers.

“Russia is fulfilling its contractural treaty obligation to deliver the S-300 defence capabilities to Iran. It had nothing to do with the negotiations,” he said during a joint news conference with his Portuguese counterpart Rui Machete.

“I think it is the right decision that Russia has made, it is a contract that we have with Russia which is fully legal and will have no impact on the negotiations.”

Meanwhile, Iran said on Wednesday it would only accept a deal over its contested nuclear programme if world powers simultaneously lifted all sanctions imposed on it.

The comments by President Hassan Rouhani came the day after US President Barack Obama was forced to give Congress a say in any future accord - including the right to veto the lifting of sanctions imposed by US lawmakers.

Meanwhile, US Secretary of State John Kerry Wednesday welcomed a compromise with Congress on giving lawmakers a say on any final deal on Iran’s nuclear programme, with negotiations set to resume next week.

Kerry said the measure approved Tuesday by the Senate Foreign Relations Committee, which raises the threshold for critics in Congress to block any accord with Tehran, made him “confident” ahead of a June 30 deadline. “Yesterday there was a compromise reached in Washington regarding congressional input,” he told reporters at a G7 foreign ministers’ meeting in Germany.

“We are confident about our ability for the president to negotiate an agreement and to do so with the ability to make the world safer.”

In a display of bipartisan cooperation on what has been a divisive issue, the Senate Foreign Relations Committee voted 19-0 in favour of allowing lawmakers to review and potentially reject the final accord.

However under the legislation, which now heads to a full Senate debate and vote, the total review period would be reduced to 52 days, from the 60 days in earlier drafts.

Contentious language obliging President Barack Obama to certify to Congress that Iran was not engaging in terrorism was also removed from the bill.

Global powers must resolve a series of technical issues by the June 30 deadline for a final deal, including the steps for lifting sanctions on Iran, and remaining questions over the possible military dimensions of its nuclear programme.

Iranian President Hassan Rouhani on Wednesday also played down the threat of US congressional action against a possible nuclear deal, saying Tehran is not negotiating with the lawmakers but with world powers.

The host of the G7 meeting in the northern German city of Luebeck, German Foreign Minister Frank-Walter Steinmeier, said talks between representatives of the United States, Britain, France, China, Russia, Germany and Iran “on a final agreement will begin next week”.

He did not cite a date or location.

The aim is to pave the way for “a meeting at the level of the foreign ministers at a later point in June” to seal a final accord.

Many of the countries involved in the Iran negotiations were attending the two-day G7 meeting in Luebeck, which also addressed a range of global crises including Ukraine, Yemen and the struggle against Islamic State militants.

Steinmeier said it was the “shared hope” of G7 partners that a deal with Iran on its sensitive nuclear work “would provide an incentive to reach solutions in other (regional) conflicts”.

In their final declaration, the G7 ministers called on Iran to play “a responsible and constructive role in its regional environment”.

They urged Tehran “to actively contribute to the efforts of the international community to achieve a political solution in Syria, to support the process of reconciliation in Iraq and to reject all acts of terrorism and terrorist groups”.

“We also call on Iran to assist in facilitating dialogue between the legitimate authorities and the Huthis in Yemen in order to enable a de-escalation of the crisis.”

The conflict in Yemen, though rooted in local rivalries, has become a proxy battlefield for regional rivals Saudi Arabia, which is Sunni-ruled, and mainly Shiite Iran.

Iranian Foreign Minister Mohammad Javad Zarif said Tuesday in Madrid that his country has proposed a peace plan for Yemen that calls for a ceasefire followed by talks by all sides that would be mediated by foreigners.