The White House criticized Russia on Wednesday for its "red-carpet welcome" of Syrian President Bashar al-Assad in Moscow.
Spokesman Eric Schultz said such treatment was at odds with Russia's stated goal of helping to arrange a political transition in Syria.
“We view the red-carpet welcome for Assad, who has used chemical weapons against his own people, at odds with the stated goal by the Russians for a political transition in Syria,” Schultz said.
U.S. officials said they were not surprised by the Assad visit to Moscow, even though the Kremlin kept it a secret.
Assad returned home Wednesday from what was believed to have been his first overseas trip since 2011, when peaceful protests against his government began to grow into today's civil war. The fighting so far has killed at least 240,000 people. Many of the victims have been civilians.
Assad held talks at the Kremlin with Russian President Vladimir Putin. He thanked Putin for Russia's intervention, saying it had stopped the spread of more "terrorism" in Syria. "Terrorists" is the word Assad uses to refer to the rebels.
Russia entered the war in Syria three weeks ago with the stated intent of destroying Islamic State. But the U.S. has said Russian airstrikes have instead hit other rebel groups and are actually meant to prop up Assad.