The US and Iraq are negotiating a new agreement to provide a legal basis for US troops to stay in Iraq after December 31, when their UN mandate expires.

They are also negotiating a long-term strategic framework agreement on political, diplomatic, economic, security and cultural ties.

"We have reached a dead end, because when we started the talks, we found that the US demands hugely infringe on the sovereignty of Iraq, and this we can never accept," al-Maliki said during a visit to Jordan on Friday.

In his first detailed comments on the talks, he said Iraq objected to Washington's insistence on giving its troops immunity from prosecution in Iraq and freedom to conduct operations independent of Iraqi control.

"We can't extend the US forces permission to arrest Iraqis or to undertake terror fighting in an independent way, or to keep Iraqi skies and waters open for themselves whenever they want," al-Maliki said.

"One of the important issues that the US is asking for is immunity for its soldiers and those contracting with it. We reject this totally."

Officials in Baghdad and Washington said two weeks ago that the Status of Forces Agreement, or Sofa, would be settled by the end of July.

But Khalaf al-Olayan, a Sunni bloc leader in Iraq's parliament, told Al Jazeera: "It's not possible to finalise an agreement of this importance so quickly.

"The timing is extremely tight.

"[The proposed agreement] has to be presented first to the Iraqi parliament or put to a national referendum because there are very important issues regarding national sovereignty."

George Bush, the US president, said on Wednesday that he was confident of reaching an agreement with Iraq.

Members of Iraq's parliament say they are facing US pressure to meet deadlines on issues that should take months to resolve.

Last week a majority of them wrote to the US congress rejecting a long-term security deal with Washington if it is not linked to a requirement that US forces leave.

"The majority of Iraqi representatives strongly reject any military-security, economic, commercial, agricultural, investment or political agreement with the United States that is not linked to clear mechanisms that obligate the occupying American military forces to fully withdraw from Iraq," the letter to the leaders of Congress said.

However, David Satterfield, the US state department's senior adviser on Iraq, has said the agreement is on schedule.

Speaking in Baghdad on Tuesday, Satterfield said: "We are confident it can be achieved, and by the end of July deadline.

"Your question may be, 'well, what if you aren't finished by then?' We believe this is do-able by the end of July, so does the Iraqi side."

Talks over the issue have been shrouded in secrecy but a senior Iraqi source told Al Jazeera that there have been several areas that have alarmed Iraqi negotiators.

In particular, Iraqis are fighting a push by the Bush administration for permanent military bases in the country and for US private security contractors to be given immunity from Iraqi law, Al Jazeera's Ghida Fakhry said.

"If the original deadline is missed, it could mean that major obstacles have emerged and that the plan to rush through a deal before George Bush steps down as president might also be in jeopardy," she said.