– President-elect Donald Trump, criticized for his friendly relations with Russian President Vladimir Putin, faces major obstacles if he tries to lift sanctions newly imposed on Russia for election hacking.

Politically, lawmakers of both parties, including Republican leaders, immediately began pressuring him to keep intact the penalties that President Obama rushed into place Thursday following months of foreign hacking.

House Homeland Security Committee Chairman Michael McCaul, R-Texas, said he looked forward to working with the incoming administration to ensure “that — in the future — our response to such aggression is timely, decisive, and forceful enough to convince our adversaries not to do it again.”

“I hope the incoming Trump administration, which has been far too close to Russia throughout the campaign and transition, won’t think for one second about weakening these new sanctions or our existing regime,” said Sen. Chuck Schumer, incoming Senate Democratic leader.

The International Emergency Economic Powers Act requires Trump’s treasury secretary to certify that the Russians have stopped hacking in order to lift the sanctions. His nominee, Steven Mnuchin, faces challenging confirmation hearings and then would have to overcome substantive hurdles if he tried to lift the sanctions.

“He can get rid of it, but it’s very difficult,” said James Lewis, who has worked at the State and Commerce departments. “They have done it in a way that’s hard to undo.”

In response to the sanctions, Trump said that “it’s time for our country to move on to bigger and better things.”

On Thursday, the Obama administration imposed sanctions against Russian intelligence services and their top officials, expelled 35 Russian officials and closed a pair of Russian-owned compounds in the United States.

Obama’s move was his latest attempt to enact policies to outlast his presidency. Trump takes over on Jan. 20.

In recent weeks, Obama has appointed dozens of people to boards, commissions and offices, pardoned or reduced the prison sentences of hundreds of federal inmates and issued numerous executive actions, including blocking the sale of new offshore drilling rights in parts of the Arctic and Atlantic.

Putin’s spokesman Dmitry Peskov said that the sanctions were designed to undermine Trump.

“We think that such steps by a U.S. administration that has three weeks left to work are aimed at two things: to further harm Russian-American ties, which are at a low point as it is, as well as, obviously, to deal a blow to the foreign policy plans of the incoming administration of the president-elect,” he said.

A senior administration official acknowledged that Trump could undo the sanctions, but argued that it “wouldn’t make a lot of sense.”

The official, who was not authorized to speak publicly, said the evidence shows a pattern of Russia intervention in the U.S. political system as well as harassment of U.S. diplomats.

“This should be of concern to all Americans,” the official said, adding that “there is no reason to believe that Russia’s activities will cease.”

Trump said at a July news conference that he’d consider lifting the sanctions imposed against Russia for its annexation of Crimea, along with suggesting that he’d be open to recognizing Crimea as Russian territory. He said at the news conference he “would be looking into that.”

“President-elect Trump has given some indications that his administration might consider lifting the sanctions aimed specifically at Russia for its interference in the Crimean region of the Ukraine,” said Lawrence Ward, a partner at the international law firm Dorsey & Whitney who focuses on U.S. national security law, international trade compliance law and licensing. “Optically, it may be more difficult for the new administration to lift these sanctions.”