US and Russia is set to hold consultations on how to implement a Syria truce on February 19.
Around 100 trucks of humanitarian aid have been delivered to five besieged Syrian towns on February 17.
"This is hopefully the beginning of the end of Syrian civilians' suffering," Almonitor quoted the UN's Jan Egeland as saying.
"This is a step forward," State Department spokesman Mark Toner told journalists at the State Department press briefing Feb. 17. "[But] I would be clear that this is just a first step in dealing with the significant problem of humanitarian assistance in besieged areas. ... The Assad regime should have allowed this access long ago."
"We are hoping to build on this access," Toner said, adding the United States was concerned Assad's regime had described the permission to let the aid convoys in as a temporary. "We obviously want to see permanent access."
"We understand the International Syria Support Group (ISSG) cessation of hostilities task force will convene Feb. 19 in Geneva under UN auspices," the US official said.
"The ISSG cease-fire task force, to be co-chaired by the United States and Russia, is supposed to include both political and military officials. Russia has been pressing for more intensive US-Russian military to military consultations on Syria, which to date the United States has been reluctant to pursue."
But the consultations between military officers would be necessary to implement any eventual cease-fire and police it, Toner said.
With progress to show on the humanitarian front, American and UN officials hope to reconvene talks by Feb. 25 between the Syrian government and opposition in Geneva that were suspended earlier this month.
"The Geneva talks [are] set to begin again ... between the opposition and regime next week, having some concrete progress to point to on the ground, whether with regard to cessation of hostilities or access to besieged areas," said US State Department Deputy Spokesman Mark Toner.
"But US officials and regional experts were cautious about prospects for a partial cease-fire to get off the ground, with the regime and its backers pursuing what they described as a strategy to seal off the Turkish-Syrian border and encircle Aleppo."