US national security adviser Jake Sullivan spoke Wednesday with his Russian counterpart, the White House said.
The call between Sullivan and Russian Security Council Secretary Nikolai Patrushev marks the highest-level known contact between the US and Russia in weeks.
Sullivan reiterated "the United States’ firm and clear opposition to Russia’s unprovoked and unjustified invasion of Ukraine," according to a statement.
"Mr. Sullivan clearly laid out the United States’ commitment to continue imposing costs on Russia, to support the defense of Ukraine’s sovereignty and territorial integrity, and to reinforce NATO’s eastern flank, in continued full coordination with our Allies and partners. Mr. Sullivan told General Patrushev that if Russia is serious about diplomacy then Moscow should stop attacking Ukrainian cities and towns. Mr. Sullivan also warned General Patrushev about the consequences and implications of any possible Russian decision to use chemical or biological weapons in Ukraine," the statement continued.