The State Department had no details to offer Thursday on whether and how it might be responding to U.N. envoy Staffan de Mistura’s urgent plea for the U.S. and Russia to help salvage the disintegrating Syrian peace talks.

De Mistura called for a “U.S.-Russian initiative at the highest level” to help enforce a March truce, according to the Associated Press. Syrian opposition groups have said they can’t enter into a political dialogue while still under attack from Syrian and Russian forces.