A senior Russian Foreign Ministry official has accused the United States of taking a "destructive" stance in bilateral relations.
Deputy Foreign Minister Sergei Ryabkov said in Moscow on February 27 that U.S. Secretary of State John Kerry had breached "diplomatic ethics" when he said earlier this week that Russian officials had "lied to his face" in denying Moscow's support for separatists in eastern Ukraine.
Ryabkov added that Washington "lacks the moral right" to make such a judgment.
Ukraine, NATO, the United States, and several western countries have accused Russia of using troops and weapons to support the rebels.
Ryabkov reiterated the Kremlin's denial of such backing.
He also warned that Russia could retaliate against potential new U.S. sanctions against Moscow -- which Kerry told lawmakers this week Washington has ready to go -- with "quite painful countermeasures."
But he said Russia might not publicize the measures it would take against the United States.