Russia meanwhile wants the gathering of the International Atomic Energy Agency's 35-nation board of governors to address the risk that possible US air strikes might hit a small nuclear reactor in Syria.
"Things have changed on the ground in Iran. We have a new government, a new president and there has been a change in tone from the Iranian government, which we recognise and welcome," one senior Western envoy said.
"By November there will have been another round of negotiations with the IAEA, we may well have another round of E3+3 talks, and so we will see whether these words have been translated into anything more concrete."
The quarterly meetings of the IAEA's board usually see Iran taken to task over its nuclear programme, which many countries, not only in the West, fear is aimed at getting atomic weapons, despite Iranian denials.
The agency's latest regular report on Iran last month showed, yet again, that Tehran is defiantly expanding its activities despite a string of UN Security Council and IAEA board resolutions demanding a suspension.
Several rounds of UN sanctions have been imposed on Iran. Additional EU and US restrictions last year began targeting its oil sector and banks.
The United States and Israel, the Middle East's sole if undeclared country with nuclear weapons, have refused to rule out bombing the Gulf country.
Numerous diplomatic initiatives over the past decade, including the last meeting between Iran and the six permanent members of the UN Security Council and Germany (the P5+1 or E3+3) in Kazakhstan in April, have failed.
The election in June of Hassan Rowhani, a former nuclear negotiator, as Iran's new president to replace the more hardline Mahmoud Ahmadinejad has however created some hope that a new push might bear fruit.
At his first press conference in August, Rowhani urged "serious" talks, and has handed responsibility for nuclear talks to the foreign ministry under the US-educated moderate Mohammad Javad Zarif.
Zarif said on Friday after a phone call with EU foreign policy chief Catherine Ashton, P5+1 lead negotiator, that Tehran wanted to "remove any ambiguity" about its nuclear work.
The two will meet during the UN General Assembly later this month ahead of a possible new round of six-party talks.
Rowhani has also appointed a new Iranian envoy to the IAEA, Reza Najafi, ahead of a meeting with the watchdog in Vienna on September 27, and former foreign minister Ali Akbar Salehi as head of Iran's Atomic Energy Organisation.
"It is in the interests of all sides to seize this opportunity created by the election (of Rowhani)," said Kelsey Davenport and Daryl Kimball from the Arms Control Association..
Lurking in the background however is the desire of US President Barack Obama to bomb Iran's ally Syria over the latter's alleged use of chemical weapons, an issue also driving a wedge between Washington and Moscow.
Russia, which opposes military action on Syria, warned last week that US strikes could have "catastrophic" consequences if a small research reactor in the Damascus suburbs were hit.
Moscow has said it will raise the issue at the IAEA meeting and has asked the agency for a risk analysis. The IAEA said over the weekend only that it had received the request and was "considering the questions raised".
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