The UN Security Council will vote Friday at 1600 GMT on a draft resolution demanding a 30-day ceasefire in Syria to allow for deliveries of humanitarian aid and medical evacuations, diplomats said.
A slightly amended text was circulated to council members, but it was unclear whether Russia would support the measure.
Russian Ambassador Vassily Nebenzia told a council meeting on Thursday that there was "no agreement" on a truce and presented a new raft of amendments.
Negotiations on the draft have dragged on as hundreds of Syrians have died in a fierce government air campaign in the rebel-held enclave of Eastern Ghouta.
Sweden and Kuwait presented the proposed measure on February 9.
The latest text softens language in a key provision to say that the council "demands" a ceasefire, instead of "decides".
It also specifies that the ceasefire will not apply to "individuals, groups, undertakings and entities associated" with Al-Qaeda and the Islamic State group. A previous version simply mentioned the two terror groups.
More than 400 people have been killed in the five-day assault by the government on Eastern Ghouta, where UN Secretary-General Antonio Guterres said 400,000 Syrians are living in "hell on earth."