Under the deal, the US and Russia are aiming for reduced violence over seven consecutive days before they move to the next stage of coordinating military strikes against the former Nusra Front and Daesh (ISIL), which are not party to the truce.
However, while the general lines of the agreement have been made public, other parts have yet to be revealed raising concerns among some of Washington's allies.
"The Russians cannot unilaterally continue to bomb saying that they are only striking terrorist groups," French Foreign Minister Jean-Marc Ayrault said in remarks confirmed by his entourage, Reuters reported.
"The agreement with the Americans, for which we don't know all the details - and that's the problem actually - makes provisions so that the Americans and Russians can check exactly location by location on a map where the terrorists we need to strike are located," he said.
"But if there is confusion... then there is a also a risk of the moderate opposition being hit. At one point we're going to be asked to support in greater detail this Russo-US plan, so to do that we will need to have all the information," Ayrault said during a visit to Ukraine.
France is a key backer of militants fighting Syrian President Bashar Assad's forces and volunteer groups, and has previously voiced its concerns over how Washington negotiates with Moscow.
As part of the deal, humanitarian aid is due to be delivered to Aleppo Friday following a withdrawal of combatants from a contested road leading to the city. Ayrault said this delivery would be crucial to assessing to the viability of the agreement.