The United States is backing the UN to take over the peacekeeping force in Sudan's Darfur region.
The African Union says it may have to withdraw troops for lack of funds
Top US diplomat Robert Zoelleck said he hoped the UN Security Council would approve the size and nature of the mission by the end of February.
Last month, Sudan said money spent on a UN force would be better used helping the current African Union one.
Mr Zoellick said 7,000 AU troops already in the war-torn region could become the core of the UN force.
Some 2m people have fled their homes in Darfur amid fighting between rebel groups and pro-government Janjaweed militias.
The New York based organisation Human Rights Watch and the International Crisis Group in Brussels have also called for UN-backed peacekeepers to be deployed swiftly in Darfur.
They say militia are continuing to operate with impunity in the region.
It is thought that a UN force would be better equipped and have a tougher mandate.
Mr Zoellick, Deputy Secretary of State, said on Wednesday the US would use its month-long presidency of the Security Council to push through the proposals, Reuters news agency reports.
"February is a short month, as you know, so we're trying to push forward on this," he said.
On Tuesday, UN Secretary General Kofi Annan said the AU had signalled that it wanted its troops to be part of a UN peacekeeping operation.
Meanwhile, AU-chaired peace talks in Nigeria have been marred by violence between the rebels, after some delegates were attacked when they defected from one faction to another.