EU sets stage for Iran-US breakthrough

British foreign minister William Hague, who also met Zarif, said: "The United Kingdom does not seek a confrontational relationship with Iran and is open to better relations."

He noted that if Iran takes "concrete steps" on nuclear non-proliferation then "I believe a more constructive relationship can be created."

France's Laurent Fabius said recent statements by Iranian President Hassan Rohani "have shown a certain evolution and it's not the same tone as his predecessor."

In terms of the UN schedule, Rohani is to talk with French leader Francois Hollande on Tuesday in the first top-level France-Iran meeting since 2005.

Rohani will also address the UN plenary chamber on Tuesday afternoon in a speech expected to offer new concessions on Iran's uranium enrichment programme.

He said in a foretaste on his Facebook page on Monday: "I and my colleagues will take the opportunity to present the true face of Iran as a cultured and peace-loving country … The West should opt for the path of talks and co-operation and consider mutual interests."

Meanwhile, Zarif is to sit down with foreign ministers from China, France, Germany, Russia, the UK and, crucially, the US, for talks on the nuclear dossier on Thursday.

There is even talk that Rohani and US President Barack Obama might meet for a symbolic handshake in the margins of the UN event.

Back in 2007, the then US secretary of state Condoleezza Rice had a brief encounter with Zarif's predecessor, Manouchehr Mottaki, at a conference in Egypt.

But Iran and the US have shunned direct contact since Iran's Islamic revolution in 1979, which ousted a US puppet government and which led to the sacking of the US embassy in Tehran.

In terms of concrete steps, Iran on Monday granted amnesty to 80 political prisoners held since a failed uprising in 2009.

Last week, it released 11 other dissidents, including Nasrin Sotoudeh, the 2012 winner of the EU's Sakharov Prize for human rights.

Looking back, Iran's former president Mohammad Khatami said in an op-ed in the Guardian on Monday that Iran and Western powers narrowly failed to reach a nuclear deal during his time in office some 10 years ago.

He noted that the US invasion of Iraq in 2003, as well as Israeli "scepticism," "sabotaged the chance," however.

There is no shortage of Israeli scepticism this time around as well.

Israeli leader Benjamin Netanyahu has described Rohani as a "wolf in sheep's clothing" in one of several taunts since Rohani came to power in August.

Netanyahu has also indicated that when he speaks to the UN chamber on Friday he will tell Iran to dismantle nuclear facilities in Fordo, Natanz and Arak if it wants peace.

For its part, the US opted for gentler rhetoric on the eve of Rohani's UN address.

"We hope that the new Iranian government will engage substantively with the international community to reach a diplomatic solution to Iran’s nuclear program," US foreign relations spokeswoman Jen Psaki said.

"We remain ready to work with Iran should the Rohani administration choose to engage seriously," she added.