This was a key demand of the Shias, whose leaders set their face against the US plan to give control of the country to panels of "the great and the good".

Last night the UN envoy, Lakhdar Brahimi, said power should still be handed over to the Iraqis this summer as planned. But his aides said there would not be time to hold "credible elections" before then.

He distanced himself from the controversial US plan, hinting that it would have to be drastically rewritten or shelved.

"I think the people who put it together realise that it needs at the very least to be improved considerably," he said.

It now seems likely that elections will be held later this year, after power is passed from the coalition authority to an interim Iraqi administration but well ahead of the December 2005 date originally set by the US-led administration.

"What I think everybody is agreed on is that elections are terribly important, and holding reasonably credible elections is also extremely important," Mr Brahimi told a news conference in Baghdad. "The date of the elections has to be consistent with this requirement."

He said more steps needed to be taken before a ballot, in cluding the writing of an electoral law.

Mr Brahimi has spent the past week meeting Iraqi political and religious leaders to discover whether it is safe, or possible, to hold elections before June.

On Thursday he met the most senior Shia cleric, Grand Ayatollah Ali al-Sistani, who has led the call for immediate direct elections.

Iraq's Shia Muslims are in the majority, but for centuries the country has been run by the Sunnis. Under Saddam, the Shias suffered particular persecution, and they are now pressing hard for the right to take part in government.

Tens of thousands of Shias have demonstrated in public in recent weeks, demanding the quick elections they know would put them in power.

The UN envoy also gave the first public warning of the risk of civil war at a time when the insurgency bombing campaign has intensified.

"I am a little bit disturbed and a little bit uneasy, because there are very, very serious dangers," he said.

Mr Brahimi, a former Algerian foreign minister, helped mediate in the civil wars in Lebanon and Yemen in the 90s.

"Civil wars happen because people are reckless, because people are selfish, because groups think more of themselves than they do of the benefit of their country," he said.

Negotiations will now begin on forming an Iraqi authority that can take power on June 30.

If the plan for regional caucuses is shelved, some on the US-appointed governing council want power transferred to them.

Some have suggested enlarging the council to include other parties, and extending its authority.

Others have spoken of a technocratic interim authority.

Mr Brahimi gave little away about the shape the new administration might take.

"The only thing I know is that what we are talking about is something provisional, something that is not going to last very long, something that is not going to have very extensive powers," he said.

He will report his findings to Kofi Annan, the UN secretary general, within 10 days. The UN will then work with the US to draw up a new political programme.

While the Shias are clamouring for a quick vote, the Sunnis are increasingly opposed to elections, fearing that they will produce a government dominated by the Shia clergy. Iraq's secular liberals are equally worried that Sunni and Shia clerics will seek to repeal the country's many secular laws.

Although the UN is eager to return to Iraq to try to recon cile these divides, the problem of security remains.

Last August the then UN envoy, Sergio Vieira de Mello, was one of the 22 people killed when the UN's headquarters in Baghdad was hit by a suicide truck bomb. This week more than 100 Iraqis have been killed by suicide bombs.