Crucial nuclear talks due to take place next week between Iran and world powers have run into disagreement over the host city, with Tehran on Wednesday saying it no longer wants Istanbul as the venue.

Instead, according to Iraq's foreign ministry, Iran has asked Baghdad to host the April 13-14 negotiations.

That contradicts an announcement by US Secretary of State Hillary Clinton last weekend that the talks would be held on those dates in Istanbul -- the Turkish city which Iran had initially proposed as its favoured option.

Iranian Foreign Minister Ali Akbar Salehi stressed on Wednesday that "this issue has to be agreed on by both sides," explaining that "Baghdad and also China were proposed" as venues, according to the website of Iranian state television.

The down-to-the-wire wrangling over the location was a sign of the high-stakes negotiating positions ahead of the talks involving Iran and the P5+1 group comprising the five permanent UN Security Council members plus Germany.

Iran's sudden about-face on Istanbul also hinted at animosity towards Turkey over its position on Syria, the Islamic republic's principal ally in the Middle East.

Turkey, which has called for Syrian President Bashar al-Assad to step down to end the year-long bloody strife in his country, on Sunday hosted a "Friends of Syria" conference sympathetic to Syrian rebels and criticised by Tehran.

Turkey, a NATO member, has also joined a US-imposed sanctions push to cut purchases of Iranian oil.

"Turkey is now excluded," Aladin Borujerdi, the head of the Iranian parliament's foreign affairs commission, told the Iranian channel Al-Alam.

"That is the position of parliament and the government. We have proposed Baghdad, and if the other side accepts, it will be Baghdad," he said.

"Taking into account the extremist and illogical position of Turkey on Syria and the recent conference on Syria, Turkey has de facto lost any competence to host the meeting," Borujerdi added.

A Turkish diplomat in Ankara speaking to AFP on condition of anonymity said his country had been ready to welcome the talks but "we didn't receive any formal demand from both sides and so we didn't commit to anything concrete."

Salehi, who had said several times last month that Istanbul would be the "best place" for the Iran/P5+1 talks, explained: "Holding negotiations in Istanbul was our preliminary suggestion which the Europeans first rejected and later accepted. But by that time we had other countries in mind."

He added: "More important than the date and the venue is the topic of discussions. And I think that the upcoming talks, compared to the ones in the past, will be better and progress will be made."

The last round of talks between Iran and the P5+1 was held in Istanbul in January 2011 and ended in failure.

The new round of negotiations is seen as an important opportunity to lower tensions over Iran's nuclear programme that have been coloured by threats from Israel and the United States of military action.

Washington and its allies believe Iran's nuclear activities include a drive towards atomic weapons capability and have imposed a raft of sanctions to punish Tehran.

Iran denies there is any military component to its programme and says it will not bow to sanctions pressure.

Iraq's foreign ministry issued a statement saying an Iranian delegation led by deputy nuclear negotiator Ali Baqeri "expressed the desire for Iraq to host the international meeting on the Iranian nuclear file."

It said it "welcomed the Iranian proposal" and Iraqi Foreign Minister Hoshyar Zebari "confirmed that he will undertake the necessary contacts with the relevant parties on the proposal."

If agreement were reached to hold the talks in the Iraqi capital, the date for the talks would be "April 14, 2012," it said.

After Clinton's announcement the talks would take place in Istanbul, EU diplomats cautioned the venue was still under discussion.

Russia also said "the date and the place of the meeting have not been definitively set."

Clinton on Tuesday seemed to step away from her announcement, saying that she expected the talks "will commence within the next several weeks."

She added: "We're hoping that there will be a path forward that gives the Iranians a reason to believe that it is in their national interest not to pursue their nuclear programme."

burs/rmb/hc