State Department spokesperson Matthew Miller issued the warning at a briefing in response to questions about the meeting in Russia between Russian President Vladimir Putin and North Korean leader Kim Jong Un.

“We have taken a number of actions already to sanction entities that brokered arms sales between North Korea and Russia and we won’t hesitate to impose additional actions if appropriate,” Miller said.

It was troubling that Russia and North Korea are discussing increased cooperation that could violate U.N. Security Council resolutions, he said.

“When you see what looks to be increased cooperation and probably military transfers, that is quite troubling and would potentially be in violation of multiple U.N. Security Council resolutions,” Miller said.