WASHINGTON — A bipartisan group of senators is sponsoring legislation to explicitly prohibit the president of the United States from withdrawing from NATO without Senate approval.

Sens. Tim Kaine, D-Va., and Cory Gardner, R-Colo., with Senate Armed Services Committee Chairman John McCain, R-Ariz., and ranking member Jack Reed, D-R.I., introduced the bill Thursday. President Donald Trump has repeatedly questioned the trans-Atlantic alliance.

A separate House bill would prohibit funds from being used to withdraw the U.S. from NATO. It’s sponsored by California Reps. Jimmy Panetta, a Democrat, and Steve Knight, a Republican. Both sit on the House Armed Services Committee.

The bills are the latest moves by Congress to reaffirm support for NATO in the wake of Trump’s polarizing performance at a NATO summit in Brussels, where he pressed allies over burden-sharing, and following a meeting in Helsinki, Finland, where he seemed to side with Russian President Vladimir Putin over the U.S. intelligence community’s assessment Russia meddled in U.S. elections.

Earlier this month, the Senate passed legislative language to reaffirm support of NATO that passed the Senate, 92-2.

“Regrettably, President Trump’s mistreatment of our closest allies has raised doubts about America’s commitment to the transatlantic alliance and the values of defense,” McCain said in a statement, adding that the bill was “urgently required.”

“In the future, the Senate must be prepared to defend its constitutional role,” he said.

The Senate bill, if passed, would require the president to seek the advice and consent of the Senate to modify or terminate U.S. membership in NATO, and it formalizes the Senate’s opposition to withdrawing from the treaty. If the president attempts to withdraw from NATO without Senate approval, this bill also authorizes the Senate legal counsel to challenge the administration in court.

Article II, Section 2 of the Constitution declares that the president “shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur.”

“Just as it was required to join NATO, Senate approval should be required before this President — or any U.S. President — can withdraw,” according to a statement by Kaine, who is a member of the Senate Armed Services and Foreign Relations committees.

While Trump has not publicly threatened to withdraw from NATO, his comments have stoked fears among allies. Beyond criticism of burden-sharing, he appeared to question Article 5, the alliance’s mutual-defense clause, in a recent Fox interview.