Secretary of State Rex Tillerson expressed disappointment Friday at Russia's hostile reaction to missile strikes against Syria, but said Moscow's trenchant support for the regime was unsurprising.

"I'm disappointed in that response from the Russians because it indicates their continued support for the Assad regime," said Tillerson, who is expected to make a difficult trip to Moscow next week.

"In particular," he said, the response showed the Kremlin's "continued support for a regime that carries out these kinds of horrendous attacks on their own people."

"I find it very disappointing but sadly I have to tell you not all that surprising," Tillerson added.