Officials on Wednesday said Washington had every intention of adhering to the 30 June handover agreed by the US-led occupation and the Iraqi interim leadership but added there was "room" for the date to be put off if the UN desired.
"The intention is not to come up with something post-30 June, but we have to leave a little room for the UN to come up with what they think best," a senior State Department official said.
"We will see what they come up with and we will consider seriously whatever they have said," the official added.
UN chief Kofi Annan said on Tuesday he would soon be sending a team of experts to Iraq in a bid to resolve the increasingly contentious dispute over how power should be transferred.
"We want to leave a little space for the UN to come back with whatever they think best"
Under an earlier agreement between the US-led occupation authority and the US-appointed Iraq Governing Council, power will be transferred on 1 July to a provisional authority named by a transitional assembly.
But the plan has triggered strong protests from Iraq's majority Shia community, which is demanding direct national elections.
The US insists elections are impractical in the timeframe allotted. But confronted with such opposition, it has said it is ready to consider "refinements" to the initial plan and asked Annan to come up with suggestions.
During meetings with US President George Bush and Secretary of State Colin Powell on Tuesday, Annan indicated he "might have some ideas on the 30 June date."
US State Department spokesman Richard Boucher said changing the handover date was "not policy" and that every effort was being made to keep the deadline.