The two countries reiterated on Monday that sanctions on the four men could complicate peace talks in Abuja, Nigeria to end the three-year conflict in Darfur which has caused about 180,000 deaths - most from disease and hunger - and displaced two million people.
The African Union, which is mediating the talks, has set an April 30 deadline for a peace deal.
If approved, the sanctions would be the first imposed by the UN Security Council since it adopted a resolution in March 2005 authorising an asset freeze and travel ban on individuals who defy peace efforts, violate international human rights law, or are responsible for military overflights in Darfur.
"We very well could vote tomorrow," Richard Grenell, spokesman for the US Mission to the UN, said on Monday evening.
When asked whether they would veto the resolution or abstain, Konstantin Dolgov, Russia's deputy UN ambassador, and Wang Guangya, China's UN ambassador, said they had not yet received instructions.
"We think that we should not take any steps which could have a negative bearing on the Abuja peace talks," Dolgov said. "But at the same time, decisions that have been previously taken by the council, they are to be implemented. It's a matter of how and when."
Wang said China wants "nothing until Abuja talks" are completed.
US officials have said they hope to ease Russian and Chinese concerns by having the Security Council approve a statement expressing support for the Abuja talks at the same time the resolution is put to a vote.
The draft resolution names four men who would face sanctions:
Russia and China oppose the plan
to impose sanctions on Sudan
Gaffar Mohamed Elhassan, former commander of the Sudanese air force's western region. Council diplomats said he had direct operational command of Sudan's army in Darfur from 2004-2006 and co-ordinated operations between government forces and the Janjaweed which resulted in scores of attacks on non-Arab villages. He was also a supplier and conduit for weapons getting into Darfur, the diplomats said.
Sheikh Musa Hilal, chief of the Jalul tribe in North Darfur. He is a Janjaweed leader and some of the worst atrocities, including rape, robbery and the burning of villages, occurred under his command, with government assistance. His record dates back to 1997 when he was jailed for killing 17 people in Darfur, according to the diplomats, who spoke on condition of anonymity because they were not authorised to speak publicly.
Adam Yacub Shant, a commander in the rebel Sudan Liberation Army. Diplomats said he violated the ceasefire in July 2005 by ordering SLA soldiers to attack government forces in Darfur. The attack killed three government soldiers.
Gabril Abdul Kareem Badri, a rebel commander in the National Movement for Reform and Development. Diplomats say he kidnapped members of the African Union force in Darfur in October and in November threatened to shoot down AU helicopters.
Decades of low-level tribal clashes over land and water in the Darfur region erupted into large-scale violence in early 2003 when ethnic African tribes took up arms, accusing the Arab-dominated central government of neglect.
The three-year-old conflict has
caused over 180,000 deaths
The government is accused of responding by unleashing Arab tribal militias known as Janjaweed to murder and rape civilians and lay waste to villages - a charge it denies.
An April 2004 ceasefire has been all but ignored, and seven rounds of talks since then have yielded little result.
AU mediator Salim Ahmed Salim told the council last week the current talks offer the best chance of reaching a peace deal by April 30 though none of the warring factions have offered major concessions so far.