Lawmakers in both parties appear wary of President Donald Trump's threat to pull the United States from the North American Free Trade Agreement, an apparent move to pressure a reluctant Congress to approve his replacement to the longstanding trade pact.

"I think we should see if we can get it passed first," Sen. John Barrasso, R-Wyo., said on NBC Sunday. "I want to see how many Democratic votes come on board for this."

Sen. Sherrod Brown, D-Ohio, said he will not support the new trade deal as it now stands because it "doesn't live up" to the president's promises to help workers and halt outsourcing. He called Trump's threat "not particularly helpful."

Trump has been touting the new version of NAFTA he has crafted with the leaders of Mexico and Canada. The deal, which the president has rebranded the U.S.-Mexico-Canada Agreement (USMCA), would replace the 1994 agreement, which created a free-trade zone among the three countries.

"It's been so well reviewed I don't expect to have very much of a problem," Trump said while ceremonially signing the deal on Friday.

But Congress — along with the Canadian and Mexican legislatures — must agree to the deal before it would go into effect. Lawmakers from both parties, including Sen. Patrick Toomey, R-Pa., said last week that they would oppose it barring significant revisions.

Trump appears aware of the resistance he faces. He threatened late Saturday to cancel NAFTA, in a move to heighten pressure on Congress to approve the new deal.

"I'll be terminating it within a relatively short period of time," Trump said aboard Air Force One en route from Buenos Aires, where he had signed the new trade pact."We get rid of NAFTA. It's been a disaster for the United States."

Brown, who has long opposed NAFTA, said he wants to return to negotiations with Canadian and Mexican leaders on the replacement agreement. "We've got to do this right," the Democratic senator told "Meet the Press." "These rules so far don't get us where we need to get to stop the outsourcing of jobs, to protect the dignity of workers."

Barrasso, who has called the USMCA a "major step forward," did not criticize the president for threatening to cancel NAFTA.

"I'm a free trader, I'm a fair trader," Barrasso said when pressed to respond to the threat. "I think the president has proven to be a successful trader ... everything the president has promised, he has delivered on."