President Donald Trump on Wednesday called the Russia sanctions legislation he signed into law "significantly flawed".
He urged Congress to not use the measure to hinder US efforts to resolve the Ukraine conflict with its European allies.
"While I favor tough measures to punish and deter aggressive and destabilizing behavior by Iran, North Korea, and Russia, this legislation is significantly flawed," the president said in a statement.
“In its haste to pass this legislation, the Congress included a number of clearly unconstitutional provisions.”
The president confirmed he had signed the bill, which imposes tough measures to “punish and deter bad behaviour by the rogue regimes in Tehran and Pyongyang” and enhances existing sanctions on Moscow.
But he said “the bill remains seriously flawed — particularly because it encroaches on the executive branch’s authority to negotiate”.
Mr Trump added that "by limiting the Executive's flexibility, this bill makes it harder for the United States to strike good deals for the American people, and will drive China, Russia, and North Korea much closer together"
But he said he signed the bill “for the sake of national unity”.