US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov are in Munich to discuss Syria.
Both agree a truce is essential to help resurrect suspended peace talks between the Syrian government and the opposition.
Moscow has suggested a March 1 ceasefire.
The US and others believe that will give Assad, backed by Russian fighter planes, time to crush the moderate rebel army.
In response Washington wants an immediate end to the fighting so talks can resume on February 25.
Both parties have been reluctant to predict whether any kind of agreement is remotely possible.
Lavrov and Kerry are due to hold a news conference at 21.30 CET, follow it on euronews.