The Iraqi Cabinet dealt a blow yesterday to a draft agreement to allow US forces to stay in Iraq beyond the end of the year, demanding changes to the document to make it more acceptable.

The nature of the amendments were not specified, but Iraqi MPs said there are concerns about the lack of a guaranteed date for US forces to withdraw. Another worry is whether Iraqi courts would in practice be able to try US soldiers who commit serious crimes. There are even gripes about differing interpretations in parts of the US and the Arabic versions of the draft accord.

The Cabinet's decision, following a five-and-a-half-hour meeting, is a major setback for the Bush administration, which wants to seal the accord before a United Nations Security Council mandate, authorising the presence of foreign forces in the country, expires on December 31.

It is also a problem for Britain, which aims to base its status of forces agreement with Baghdad on the US-Iraq pact.

Ali al-Dabbagh, the Iraqi Government spokesman, said: "The Cabinet has agreed that necessary amendments to the pact could make it nationally accepted."

Ministers would continue to discuss the issue over the coming days, he said, adding that they "will give their opinions and consult and provide the amendments suggested. Then this will be given to the American negotiating team". No timeframe was offered on when this would happen.

The draft text, which sets out a conditions-based timeline for US troops to pull out of cities by next summer and leave Iraq by the end of 2011, had only last week been described as a "final draft" following months of tense negotiations.

The demand for changes further delays the approval process, throwing into question whether an agreement will be finalised by the year-end deadline. The deal should originally have been struck by the end of July. Hoshyar Zebari, the Foreign Minister, was quoted saying that it would not be approved by Parliament, which has the final say, before the US election on November 4.

As a last resort, Iraq can go to the United Nations to request an emergency extension of the mandate to buy more time -- an option that the United States does not favour.

Revealing the extent of concern about the accord, Humam Hamoudi, a leading member of parliament from the majority Shia alliance, said Nouri al-Maliki, the Prime Minister, was among those voicing doubts in recent days.

"The Prime Minister said: what [the Americans] have given with the right hand they have taken away with the left hand," Mr Hamoudi told a news conference. "For example, they said the US forces will withdraw from towns by June 2009 if the security situation permits that. But who will decide that?"

Another problem was translation. Mahmoud Othman, a Kurdish MP, said there were different interpretations of certain sections written in Arabic and English. Demands have been made for the Arabic and US translations of the text to match more accurately, he added.

Kurdish MP Adil Barwari, a member of the defence and security committee in the Iraqi Parliament, said that MPs were also worried about the chance of Iraqi territory being used to threaten neighbouring countries, something that US officials stress would never be the case.

"In addition, there is some ambiguity about some of the articles and we want clarifications from the American side. For example how will a US soldier be held accountable by Iraqi courts when they commit a crime outside their bases," he told The Times.

The only way a US service member could face an Iraqi judge, according to the draft agreement, would be if he or she committed a grave offence while off-duty and off-base.

Mr Barwani, like most Kurdish MPs, however, supports the pact in its current form, noting that he wanted "to have it today better than tomorrow".

Admiral Michael Mullen, the US Joint Chiefs of Staff, said Iraq needed the accord because its military "will not be ready to provide for their security".

He added: "In that regard there is great potential for losses of significant consequence."

In a show of force against the pact at the weekend, tens of thousands of Iraqi followers of Moqtada al-Sadr, the anti-American Shia cleric, marched through the streets of Baghdad , demanding that US forces leave the country now.

Iran, which has a close relationship with Iraq's Shia-led Government, is also opposed to the deal. General Ray Odierno, the new commander of US forces in Iraq, has accused Tehran of offering bribes to Iraqi politicians to vote against the accord. His comments to the Washington Post were later clarified to stress that he did not mean Iraqi MPs accepted the bribes.

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