Iraq's ruling Shia parties have demanded changes to a deal that would allow US troops to stay in the country until 2011.

A draft was agreed last week after months of negotiations between Baghdad and Washington, but the Shia alliance has now reviewed the document and says there are several elements it is not happy with.

The United Iraqi Alliance, which includes the Dawa party of Nuri al-Maliki, the prime minister, said on Sunday: "Beside the positive points that were included in this pact, there are other points that need more time, more discussion, more dialogue and amendments to some articles."

The deal requires US forces to withdraw at the end of 2011 unless Baghdad asks them to stay because of the security situation.

It also provides certain conditions under which US troops could be tried in Iraqi courts for serious crimes committed while off duty, a move which Iraqi officials have described as a major concession.

The Political Council for National Security - which includes al-Maliki, Jalal Talabani, the president, and other senior officials - met for about two hours on Sunday evening to discuss the pact.

"They just finished the meeting and they did not take a decision on the pact because some groups had reservations," Ali al-Dabbagh, a government spokesman, said.

He said that the only group to endorse the draft without reservations was the Kurdish bloc.

Concerns not revealed

The statement from the Shia alliance did not make clear what aspects of the draft they believed needed to be reconsidered.

Another sizeable Shia bloc in the parliament, made up by supporters of Muqtada al-Sadr, a populist leader, has opposed the plan which it argues would "stigmatise Iraq and its government for years to come".

Tens of thousands of al-Sadr's supporters took to the streets of the capital, Baghdad, on Saturday to express their objections to any deal with Washington while US forces were in the country.

Hoshiyar Zebari, Iraq's foreign minister and a Kurd, has said that Washington and Baghdad consider the draft final and would be unlikely to reopen it.

He said it would be sent to parliament for approval, but no changes would be permitted.

The so-called Status of Forces Agreement (Sofa) will provide the legal basis for a US troop presence in Iraq after the present UN mandate expires on December 31.

Parliament must approve the agreement by the end of the year, but al-Maliki needs solid support from his alliance if he expects to win approval of the agreement by a strong majority.

The United Iraqi Alliance, which also includes the Supreme Islamic Iraqi Council, holds 85 of parliament's 275 seats.

There are also concerns among some Iraqi politicians over holding a vote on the deal as it could impact negatively on them in next years's planned provincial and national elections.

British deal

On Sunday, al-Maliki said he was keen to negotiate a similar deal with the British forces deployed in southern Iraq.

Eleven decomposed bodies were found buried near Samarra [AFP]

"If the Sofa with the US is approved by parliament, it will help signing an agreement with British for their military presence in Iraq," he said in a statement after talks with John Hutton, the visiting British defence secretary.

Meanwhile, Iraqi police said that they had found 11 decomposed bodies in northern Iraq, believed to have been killed at least one year ago.

A police officer said the bodies were found in the village of Banat al-Hussein, northeast of Samarra. Eight had been found together in one mass grave on Saturday.

He said al-Qaeda had used a nearby house as a prison where they used to torture captives. 

Also in Baghdad's Zafaraniya neighbourhood early on Sunday, two civilians were killed and 10 others injured by a roadside bomb, police and medical officials said. Three police officers were among the wounded.