This was announced by U.S. Department of State spokesman John Kirby on Tuesday, Censor.NET reports.
"The United States is deeply concerned with the recent spike of violence in eastern Ukraine," he said.
He stressed that the attempt of the Russian separatists to seize additional Ukrainian territory led to the highest two-day casualty figure since June 2015.
"This is a clear violation of Russia's commitments under the Minsk agreements. And once again, we call on Russia to exercise its considerable influence over the separatists to put a stop to the violence and to allow OSCE monitors full and unfettered access," Kirby said.
He added that Washington "strongly supports" the Trilateral Contact Group's efforts to negotiate a cease-fire recommitment.