President Donald Trump has signed into a law a bill which imposes new sanctions on Russia for their alleged meddling in the 2016 election.
The bill, which was signed in private at the White House, also imposes sanctions on Iran and North Korea.
Russia denies interfering in the US election, and Mr Trump has denied colluding with Russia.
In signing the Countering America’s Adversaries Through Sanctions Act, Mr Trump attached a statement calling the sanctions “deeply flawed”.
He accused Congress, which last week overwhelmingly passed the measure and sent it to the White House, of overstepping its constitutional authority.
“Yet despite its problems, I am signing this bill for the sake of national unity,” Mr Trump’s statement says, adding that “it represents the will of the American people to see Russia take steps to improve relations with the United States”.
“I built a truly great company worth many billions of dollars. That is a big part of the reason I was elected,” he continued.
“As president, I can make far better deals with foreign countries than Congress,” he said, adding that they “could not even negotiate a healthcare bill after seven years of talking”.
Russia had already retaliated by ordering 755 people expelled from the country’s US embassy and consulates.
The sanctions, which are also in response to Russia’s annexation of Crimea, come months after President Barack Obama expelled 35 Russian diplomats.
Republican Senator Lindsey Graham praised the bill after it passed, pointing out that Mr Trump’s options were limited since there were enough votes to overcome a presidential veto.
“President Putin did something that nobody in America could do. He united the congress,” he told CNN.
Senior Russian parliamentarian Konstantin Kosachev said that Mr Trump was “capitulating” by not standing up to Congress.