Iran is hoping for advancement in talks with the UN atomic agency over Tehran's past activities as well as in negotiations with world powers on current sensitive nuclear work, the foreign ministry spokesman said Tuesday.

"We hope to see good progress" in the talks scheduled for Wednesday in Vienna between the Iranian mission and the International Atomic Energy Agency, spokesman Abbas Araqchi told reporters.

The IAEA says there is "overall, credible" evidence that until 2003, and possibly since, Iran conducted activities to develop nuclear weapons, despite Tehran's denials. It seeks to persuade Iran to grant it access to sites, documents and scientists involved in these alleged efforts.

"The talks focus on what is asked of Iran beyond its obligations," said Araqchi.

He said Iran is not "in principle" opposed to answering to IAEA demands but that a framework must first be agreed. He did not elaborate.

The meeting on Wednesday is the 10th of its kind since late 2011, when the Vienna-based IAEA published a major report on the alleged activities. Previous efforts for a deal have produced no breakthrough.

Araqchi Tuesday linked the talks with the IAEA to parallel efforts by world powers engaging Iran in a bid to curb sensitive parts of Iran's controversial nuclear programme, which Western powers suspect is aimed at developing a military capacity despite Tehran's repeated denial.

"With regards to the nuclear case, Iran's cooperation with the agency cannot be separated ... from talks with the P5+1 group" of the United States, Britain, France, China and Russia plus Germany, he said.

P5+1's representative in those negotiations is the European Union's top diplomat, Catherine Ashton, who is to meet with Iran's lead nuclear negotiator Saeed Jalili in Istanbul on Wednesday.

"We are waiting to listen to the reaction of P5+1 (through) Ms Ashton ... We hope her response is constructive."

Jalili and Ashton last met in the Kazakh city of Almaty in April. That meeting, according to Ashton, proved that Iran and world powers were still "far apart".

Iran is slapped with a series of international sanctions, reinforced by punitive measures adopted by the United Nations Security Council, over its nuclear work. Tehran insists it is within its "rights" to operate an atomic programme to produce energy.

The meetings in Vienna and Istanbul on Wednesday come as Iran prepares to hold a presidential election in June, which analysts believe has hampered progress in the nuclear talks with the P5+1.

"If the P5+1 group prefer to wait (to resume the talks) after Iran's (presidential) election, that will be their decision. But from our point of view, the talks can continue normally," Araqchi said.

Further complicating the talks is a decision by Jalili -- seen close to supreme leader Ayatollah Ali Khamenei -- to register his candidacy to contest the presidency, Iran's highest elected office.

Asked if Jalili's candidacy and election campaigning will slow the talks with the world powers, Araqchi said: "It will not be like that."

The next government, regardless of who is president, "will defend Iran's principal positions and the rights of the nation," Araqchi said.

It is Khamenei who sets Iran's line in the talks and has final say on all key state issues, including the nuclear programme.