Iran said Tuesday there was a "historic" chance to resolve a decade-long showdown over its nuclear ambitions ahead of a much-anticipated meeting of world powers at the United Nations.

"We have a historic opportunity to resolve the nuclear issue," if world powers adjust to the "new Iranian approach," Foreign Minister Mohammad Javad Zarif said in a tweet from New York, where he is attending the UN General Assembly.

His comments came a day after he met EU foreign policy chief Catherine Ashton in New York to discuss restarting nuclear talks with the so-called P5+1 group -- the United States, Britain, France, China and Russia plus Germany.

Zarif will join counterparts from the P5+1, including US Secretary of State John Kerry, at the UN headquarters on Thursday for the first-ever US-Iranian nuclear talks at the ministerial level.

Put on hold since April, the negotiations seek to allay Western and Israeli concerns that Iran is seeking an atomic weapon under the guise of its civilian nuclear drive, a charge adamantly denied by Tehran.

The Islamic state in return wants relief from draconian sanctions which have crippled its ailing economy, leading to a major devaluation of its currency and rising inflation.

Iran's newly sworn-in President Hassan Rowhani -- who has promised constructive engagement with the world -- is expected to address the General Assembly later Tuesday.

Speculation has run high that he could have a landmark encounter with US President Barack Obama on the sidelines of the summit, after the White House did not rule out a meeting between the two leaders.

Iran and the United States have held no official meetings at the ministerial level or above since the 1979 Islamic Revolution led to the severing of diplomatic ties, though there have been some high-level contacts in recent years.

A landmark meeting

An encounter between Rowhani and Obama could signal a major shift in relations between the two countries, which remain deeply divided over Iran's nuclear programme, its support for Syrian President Bashar al-Assad and its backing of regional militant groups.

But Iran's Foreign Ministry spokeswoman Marzieh Afkham said Tuesday there were no plans for such a meeting on the sidelines of the UN General Assembly.

"The right situation must present itself for this meeting. Our assessment is that it has not been presented yet," she said, adding that Iran did not want to commit to such a gesture "just for the principle of meeting each other."

Afkham said Zarif and Kerry would only meet within the P5+1 framework of talks and not in a bilateral setting.

Her remarks came after the White House on Monday said no one-on-one meetings were scheduled but did not rule out the possibility.

"We are open to engagement with the Iranian government on a variety of levels provided that they will follow through on their commitment to address the international community's concern on their nuclear program," deputy US national security adviser Ben Rhodes said.

But Zarif cautioned in a Facebook post Monday that "it should not be expected that the piling problems can be resolve in one or a few meetings."

His comments came amid increasingly vocal opposition from hardliners to any rapprochement with Washington.

Iran's armed forces deputy chief of staff General Massoud Jazayeri, a member of the powerful Revolutionary Guards, cautioned the government against trusting Washington.

"Those who are infatuated with America either do not know it or are unfamiliar with politics," he said in remarks reported by the ISNA news agency.

Washington "will make concessions only when it is faced with a powerful and steady opponent."