U.S. Sen. Bob Casey, D-Pa., plans to vote against nominating Rex Tillerson as the next Secretary of State next week, saying the two men have “basic disagreements about the most fundamental issues facing our nation.”

Casey voted against a procedural motion to move Tillerson’s nomination forward and will vote against his nomination when the final vote occurs this week.

“Many of my constituents have expressed concerns about President Trump’s nominee for Secretary of State, Mr. Rex Tillerson, and I share these concerns,” Casey said in a prepared statement issued to the media on Monday. “I carefully reviewed Mr. Tillerson’s record and testimony, and we met last week. I greatly appreciated Mr. Tillerson’s candor during our discussion of Russian aggression, U.S. interests in Syria, the rights of women and girls around the world and the importance of maintaining investments in food security, among other things. I am also grateful for his willingness to leave a lucrative private sector career for public service at this critical time in our nation’s history.”

But with the most fundamental issues facing the United States, Casey and Tillerson are in disagreement.

“I was very concerned about his refusal to say Russia is complicit in war crimes, his work to undermine U.S. sanctions following Russia’s invasion of Ukraine in 2014 and his acceptance of the Order of Friendship award from Vladimir Putin’s regime,” Casey said. “Russia must be held accountable. Its efforts to undermine our democracy and our allies must be met with resistance, not indifference. I have serious concerns about the direction that Mr. Tillerson would guide our foreign policy.”

Casey is a member of the National Security Working Group and former chairman of the Senate Foreign Relations Subcommittee on Near Eastern and South and Central Asian Affairs.