Secretary of State Rex Tillerson charged Thursday that Russia was either complicit or incompetent in its role overseeing Syria’s supposed removal of chemical weapons, on the heels of a U.S. strike on an Assad airfield in response to a deadly chemical attack.

Tillerson, speaking with reporters, said the U.S. has a high level of confidence the attack earlier this week was carried out by Assad regime aircraft and involved sarin nerve gas.

He indicated this flies in the face of agreements the Syrian government made to surrender chemical weapons under the supervision of the Russia government.

“Clearly Russia has failed in its responsibility to deliver on that commitment,” Tillerson said. “Either Russia has been complicit or simply incompetent on delivering its end of that agreement.

The comments reflect an increasingly tough tone toward Russia in recent days from the Trump administration. Earlier Thursday, Tillerson said Russia should “consider carefully” its support for the Assad regime.

Tillerson added that the response from the airstrikes has been “overwhelmingly supportive.”

Russia, aside from its ongoing support for the Assad government, was a key part of the agreement struck by the Obama administration in 2013 for Syria to dispose of its chemical weapons. The agreement helped avert any military confrontation between the U.S. and the Assad government at the time.