U.S. President Donald Trump signed a new sanctions law against Russia that Congress had approved overwhelmingly last week, criticizing the legislation as having “clearly unconstitutional” elements.

After signing a bill that runs counter to his desire to improve relations with Moscow, and which also affects Iran and North Korea, the Republican president laid out a lengthy list of concerns.

“While I favor tough measures to punish and deter aggressive and destabilizing behavior by Iran, North Korea, and Russia, this legislation is significantly flawed,” Trump said in a statement announcing the signing.

The Republican-controlled Congress approved the legislation by such a large margin on Thursday that it would have thwarted any effort by Trump to veto the bill.