Geoffe Morrell, a Pentagon spokesman, said on Wednesday that he had not "heard specifics on the possibility of reopening negotiations".
But he accused Iran, Iraq's eastern neighbour, of trying to "meddle" in US-Iraq affairs.
"In its most destructive, devious and deadly ways, it has to do with the flow of arms and weapons into Iraq," Morrell said.
"But there are, of course, counterbalancing negatives, one of which is clearly an attempt by the Iranians to undermine, undercut, derail the Sofa agreement," he said.
Robert Gates, the US defence secretary, has said that "pretty dramatic" consequences would follow if the Sofa pact falls through.
Gates said on Tuesday in Washington that the door was "pretty far closed" on further negotiations towards a security deal, although he emphasised that efforts are continuing.
Iraq's cabinet discussed the pact on Tuesday and unanimously called for changes to the draft now under review, despite US warnings that time is running out to finalise a deal.
"The consequences of not having a Sofa and of not having a renewed UN authorisation are pretty dramatic in terms of consequences for our actions," Gates said.
A status of forces agreement would replace the current UN mandate - which expires on December 31 - as the legal basis for the US military presence in Iraq.
Iraq's Political Council for National Security reviewed the draft agreement on Sunday and Monday before sending it on to the cabinet.
Iraq's Al-Sharqiya television reported that ministers from both the largest Sunni bloc - the National Concord Front - and the ruling mainly Shia grouping, the United Iraqi Alliance, wanted amendments.
|The US presence in Iraq could extend to 2011, according to the draft [AFP]
But Gates and other US officials stressed on Tuesday that the current document should be acceptable to both sides.
According to Gates, there are "only two alternatives: the Sofa or a renewed UN mandate, and going back to the UN at this point there is no assurance that you get a clean rollover".
He said there is "great reluctance" to include further changes, as the US government consults congress on the current draft.
But "if they [Baghdad or congress] were to come up with something we haven't thought of, or identify problems we missed some way, we would have to take that seriously", Gates said.
"So I don't think you slam the door shut. But I would say it's pretty far closed."
The Bush administration earlier played down the Iraqi cabinet's decision to seek further negotiations.
"We knew it was going to take a little while to get this done," Dana Perino, the White House spokeswoman, said on Tuesday.
"We knew that the Iraqis would have several steps to go through."
But Michael Mullen, chairman of the US joint chiefs of staff, said that time was running out for Baghdad to back the deal, which was originally due to have been completed by the end of July.
He cautioned that when the current UN mandate runs out on December 31, Iraqi security forces "will not be ready to provide for their security".
Mullen said Iraq risked security losses of "significant consequence" unless it approved an agreement that provides a legal basis for US forces to remain in the country.
David Isenburg, a security analyst with the Cato Insitute, told Al Jazeera that both sides are "playing hardball in the negotiations, as [one] would expect".
The draft agreement could pose a problem to Barack Obama, the Democratic candidate for the US presidency, should he win the race for the White House, he said.
"One important thing to note about this agreement is that it is currently constituted to keep US troops through to the end of 2011. Senator [Barack] Obama said that if he gets into office he will have all US troops out in 16 months. So the agreement would lock him into keeping troops beyond where he wants to be," Isenburg said.
Isenburg said an extension to the current UN mandate would only postpone examination of the differences between Baghdad and Washington.
"All they can get the the UN is, at most, a one-year extension of the current mandate. That would leave all the current issues between Iraq and the US unresolved," he said.
While the issue of the draft pact was debated in Washington, violence continued in Iraq.
A car bomb killed four people and wounded three in the northern Iraqi city of Mosul, recently the site of targeted attacks against Iraqi Christians.
The attack, which targeted civilians, occurred in the Ath-Thawra neighbourhood, said Hazim Ahmed, a local policeman.
In Baghdad, police also reported that five people had been wounded when bombs attached to two cars exploded.