Sen. John McCain (R-AZ) on Tuesday said that the resignation of Michael Flynn from his role as national security adviser raises questions about President Donald Trump’s policy toward Russia.

“General Flynn’s resignation also raises further questions about the Trump administration’s intentions toward Vladimir Putin’s Russia, including statements by the President suggesting moral equivalence between the United States and Russia despite its invasion of Ukraine, annexation of Crimea, threats to our NATO allies, and attempted interference in American elections,” McCain said in a statement.

“American policy toward Russia must be made clear and unequivocal: we will honor our commitments to our NATO allies, we will maintain and enhance our deterrent posture in Europe, we will hold Russian violators of human rights accountable for their actions, and we will maintain sanctions on Russia so long as it continues to violate the sovereignty and territorial integrity of Ukraine,” the senator added.

McCain did thank the former national security adviser for his service in his statement, but called the circumstances around Flynn’s resignation “troubling.”

“General Flynn’s resignation is a troubling indication of the dysfunction of the current national security apparatus. As our nation confronts the most complex and diverse array of global challenges since the end of World War II, it is imperative that the President select a new National Security Advisor who is empowered by clear lines of authority and responsibility and possesses the skills and experience necessary to organize the national security system across our government,” he said in the statement.