US Secretary of State John Kerry called Monday on Iran to "take advantage of this moment" following its election of a more moderate president to address concerns over its nuclear programme.

Kerry said he sought an assessment of developments in Iran during talks with Foreign Minister Salman Khurshid of India, a rare country that has warm relations with both Tehran and Washington.

"Hopefully India with its relationship could help urge the new Iranian leadership -- as well as the old leadership, the supreme leader -- to take advantage of this moment," Kerry told a joint news conference.

"We would call on the Iranians not to miscalculate about American and international commitment," he said.

"We would urge Iran to prove to the world that its peaceful nuclear programme, as they say it is, is in fact peaceful."

Khurshid voiced hope for more diplomacy, saying: "We would want to judge and test as to what the new president's intentions and inclinations are."

Iranians on June 14 overwhelmingly voted for moderate cleric Hassan Rowhani, who campaigned on promises for more social freedoms, to succeed firebrand President Mahmoud Ahmadinejad.

But foreign policy in Iran is led by the theocratic state's supreme leader, Ayatollah Ali Khamenei, who is believed to have the ultimate say on the country's nuclear programme.

Iran says that it is seeking nuclear energy, but Western countries have voiced fears that it is building an atomic bomb and Israel has not ruled out a military strike.

Iran in recent years emerged as one of the thorniest disputes between the world's two largest democracies, with New Delhi resenting US threats to impose sanctions unless India and other nations stop buying oil from Iran.

Kerry thanked energy-hungry India for cutting its purchases and said "we completely understand" New Delhi's historic relationship with Iran.