World powers are proposing to Iran to hold their first round of talks in six months on Tehran's nuclear programme already in the first half of December in Istanbul, diplomatic sources say.

"The United States want to move fast," one senior diplomat said after talks in Brussels last Wednesday among negotiators from the "P5+1" -- the United States, Russia, China, Britain, France and Germany.

"We aim to propose (to Iran) to sit around the table in the first two weeks of December... possibly in Istanbul if the Iranians accept this," he said.

A second envoy from one of the six countries involved also said this was the case.

If this proves too ambitious, then the group will push for the talks to take place in January, the diplomats said. "This fits with our aspirations," said a third.

Following the Brussels meeting, the first since US President Barack Obama was re-elected on November 6, EU foreign policy chief and P5+1 head negotiator Catherine Ashton said that the group wanted talks with Iran "as soon as possible."

US State Department spokeswoman Victoria Nuland said Washington was awaiting the outcome of a mooted upcoming "contact" between Ashton and Iran's negotiator Saeed Jalili.

In Iran, which has not so far reacted publicly to Ashton's statement from last week, Foreign Minister Ali Akbar Salehi, as quoted by the official IRNA news agency, also refused to be drawn on the date or location of a next meeting.

The Turkish city of Istanbul was where in April the P5+1 and Iran held their first talks in 15 months, seen at the time as a renewed push by Obama to ease tensions after his initial efforts early in his first term in 2009 floundered.

At the subsequent round in May in Baghdad, the P5+1 set out a list of proposals that included Iran halting its most sensitive nuclear activities, but Tehran rejected them at the next get-together in June in Moscow.

It says its nuclear drive is peaceful but many in the international community suspect its real aim is to develop atomic weapons.

The UN Security Council has imposed four rounds of sanctions on Iran which have been augmented this year by painful Western restrictions on its vital oil exports, hitting the economy hard.

-- Concessions --

With Iran feeling the pinch from sanctions and Obama now freed from the constraints of a lengthy election campaign, conditions would appear favourable to make progress.

However, it is far from clear whether the P5+1 are ready to consider easing sanctions, a key demand from Iran.

Another diplomat said Wednesday that the six powers have not yet even agreed among themselves what to put on the table, saying there was a "range of perspectives" being considered.

Signals coming out of the Islamic republic, which has used the six months since Moscow to continue expanding its nuclear programme, give little reason to expect a new spirit of compromise.

Russia's P5+1 pointman, Sergei Ryabkov, visited Tehran on November 14, and found the Iranians to be showing "not the least sign of opening up" and to be "particularly inactive and unreceptive," the first diplomat said.

"I do not think that in the end there will be enough on the table to persuade Iran to make significant concessions," analyst Mark Fitzpatrick from the International Institute for Strategic Studies in London told AFP.

"Sometime next summer we will be back in the will-Israel-bomb-Iran mode. Iran is feeling the pain from sanctions, but they felt worse pain during the Iran-Iraq war (1980-88)."

The head of Iran's nuclear authority, Fereydoon Abbasi Davani, said on Wednesday that his country would continue to expand "with force" its atomic activities, including uranium enrichment.

He also said that Iran would "soon test" its new heavy water nuclear reactor at Arak, which Western nations fear could produce weapons-grade plutonium.

Iran aims to start operating Arak in the first quarter of 2014, the International Atomic Energy Agency said this month.

Parallel diplomatic efforts between the IAEA and Iran, focused on what the agency calls "overall, credible" evidence of past weapons research work, are meanwhile set to resume on December 13 in Tehran.

A string of previous meetings between Iran and the Vienna-based IAEA, whose board is due to meet Thursday and Friday, have however been fruitless.

"I am not sure I have seen anything coming out of Tehran which suggests a significant shift in position," one Vienna-based diplomat said. "But we have to hope."

burs-stu/ssw