The issue of immunity for US military personnel is said to be a sticking point
US President George W Bush has said he is confident a deal on the future of US troops in Iraq will be approved despite amendments which Baghdad has requested.
After talks with the president of Iraq's Kurdish region, Mr Bush said officials were analysing the proposed changes to the agreement on US forces.
"We obviously want to be helpful and constructive without undermining basic principles," he told Massoud Barzani.
Washington had previously said the pact was "final" and could not be amended.
Iraqi government spokesman Ali al-Dabbagh said the proposed changes would ban US forces in Iraq from attacking any neighbouring countries - three days after a raid on Syria that Damascus says killed eight civilians.
Iraq also wants greater clarity of what jurisdiction Iraqi law has over major crimes committed by US troops when they are off duty and off base, Mr Dabbagh said.
On Tuesday, the Iraqi cabinet authorised Prime Minister Nouri Maliki to re-open talks with the US on the pact, which would allow US forces to stay in Iraq after their UN mandate expires on 31 December.
Speaking to reporters after meeting Mr Barzani at the White House, President Bush confirmed the US had received the Iraqi government's proposed amendments to the Status of Forces Agreement (Sofa).
"I informed the president we received amendments today from the government, we're analysing those amendments, we obviously want to be helpful and constructive without undermining basic principles," he said.
"And I remain very hopeful and confident that the Sofa will get passed."
State department spokesman Sean McCormack said that although the US would consider Baghdad's proposed changes, "the bar to any revisions is very high".
"All of that said, this is a serious negotiation process on a serious issue and we will take seriously any comments from the Iraqis. We will do a thoughtful, thorough review of them and then provide them a response," he added.
Correspondents say the issue of immunity for US military personnel and contractors was a key sticking point in negotiating the pact in the first place.
The draft is said to grant Iraqi judicial authorities limited ability to try US troops and contractors for major crimes committed off-duty or off-base - and only then if a joint US-Iraqi committee agrees.
The Iraqis have reportedly also raised concerns about the provisional date of 2009 set for US withdrawals from Iraqi towns and cities, and the date of 2011 for withdrawing from Iraq as a whole.
About 144,000 of the 152,000 foreign troops deployed in Iraq are US military personnel.
In an interview with the BBC, Iraq's Foreign Minister Hoshyar Zebari said some of the amendments the government had agreed to seek were substantive.
He said they included Iraq's demand to have the right to inspect US military bases and the mailbags going to and from them.
Mr Zebari said the suspension of US operations would be very bad for Iraq
"The Americans have accepted to look seriously into this amendment. Some of them, actually, are language-related formulations, not substantive, but some other amendments are substantive changes, which I personally doubt will go down well with the American side," he said.
If the agreement was not signed before the end of the year, Mr Zebari said there would be very serious military and economic consequences.
"We've been told by the American side very clearly that they will freeze all their operations, military operations, against terrorists. They will freeze all the assistance and aid and training for the Iraqi security forces," he said.
"They will suspend all economic and reconstruction projects that the US military is doing... if they are not involved. This would really be very bad news for the stability of Iraq and of the region."
The BBC's Jim Muir in Baghdad says that although Washington has agreed to examine the Iraqi proposals, there is clearly little appetite for making substantive changes.
The elements which the Iraqis want to introduce may well be beyond the limits of the US negotiators, which means that when the draft is returned to Baghdad, the cabinet will have to take it or leave it, our correspondent says.
Even if it approves the draft, which is by no means certain, it is bound to have a very rough ride in the Iraqi parliament, where Shia and Sunni factions have been either highly critical or rejected it outright, he adds.