UNITED NATIONS - UN Secretary General Ban Ki-moon told Iran’s supreme leader and president on Wednesday that “concrete” progress is needed to end the showdown over their country’s nuclear drive, a UN spokesman said.

Ban also had a tough message for Ayatollah Ali Khamenei and President Mahmoud Ahmadinejad on human rights, their caustic comments on Israel and Iran’s involvement in the Syrian civil war, UN spokesman Martin Nesirky told UN correspondents from Tehran.

The UN leader “conveyed extremely clearly and in no uncertain terms” international expectations on the nuclear dispute and a range of other topics which have led to international efforts to isolate the Islamic state, Nesirky said.

Ban went to Tehran to attend the Non-Aligned Movement summit in the face of opposition from Israel and the United States. He called for “concrete steps to address the concerns of the International Atomic Energy Agency and to prove to the world that its nuclear program is for peaceful purposes.”

The United States and its European allies accuse Iran of seeking a nuclear bomb and stonewalling efforts by the UN atomic agency to get firm information on the research which the Tehran government has insisted is peaceful. Talks between Iran and the United States, Russia, China, Britain, France and Germany have failed to start serious negotiations on ending the showdown.

In his separate meetings with Khamenei and Ahmadinejad, Ban “regretted that little tangible progress has been achieved so far during those intensive talks” and added “that the talks needed to be serious and substantive.” Ban also condemned what Nesirky called “recent rhetoric we have heard from all kinds of quarters” about a possible Israeli or US military strike on Iranian nuclear facilities.

But the UN leader took the Iranian leadership to task over their comments on Israel.

The leaders of India, Afghanistan and the Palestinian Authority flew to Tehran on Wednesday ahead of a two-day Non-Aligned Movement (NAM) summit that Iran is boasting shows its international heft.

Nearly a dozen of the 36 heads of state or government Iran says are confirmed to attend the Thursday-Friday event have arrived, according to state media.

Morsi’s appearance will be the first by an Egyptian president since Iran’s Islamic revolution in 1979 - the year that Cairo signed a peace accord with Israel.

The NAM is a 120-member organisation founded in the height of the Cold War as a grouping supposedly independent of the rival American and Soviet blocs.

Although it has struggled to stay relevant in the decades since the fall of the Berlin Wall, Iran is keen to portray it as a diplomatic counterweight to US influence and in its showdown with the UN Security Council over its disputed nuclear programme.

Leaders already reported to have arrived in Tehran include Afghan President Hamid Karzai, Bangladesh PM Sheikh Hasina, Benin President Thomas Boni Yayi, Bhutanese PM Jigmi Thinley, Cambodian Prime Minister Hun Sen and Indian Prime Minister Manmohan Singh. Others are Gabonese President Ali Bongo Ondimba, Lesotho’s PM Thomas Thabane, Mongolian President Tsakhia Elbegdorj, Swazi PM Barnabus Sibusiso Dlamini and Syrian PM Wael al-Halqi.

Palestinian president Mahmud Abbas was also seen arriving.

, getting past a dispute that saw Iran exclude his Gaza rival, Hamas prime minister Ismail Haniya, after he threatened to boycott the summit.

North Korea’s ceremonial head of state, parliamentary leader Kim Yong-Nam, was also in the Iranian capital, representing his country’s top leader Kim Jong-Un.

Others that Iran says are confirmed to yet show up for the summit include Iraqi Prime Minister Nuri al-Maliki, Lebanese President Michel Sleiman, Pakistani President Asif Ali Zardari, Sri Lankan President Mahinda Rajapaksa, Sudanese President Omar al-Bashir and Zimbabwe’s President Robert Mugabe.