President Trump touted the 11th-hour overhaul of a trade agreement among the United States, Mexico and Canada in a Rose Garden news conference on Monday. The White House announced the deal an hour before a deadline of midnight on Sept. 30

The president celebrated the new deal — the "U.S., Mexico, Canada agreement, called USMCA" — as keeping a campaign promise to renegotiate the North American Free Trade Agreement. Mr. Trump has long blasted NAFTA as perhaps the worst deal ever made. As the Sept. 30 deadline approached, it appeared less likely that the U.S. would reach an agreement to keep Canada in a trilateral trade agreement.

Asked about the greatest concession the U.S. made in the agreement, Mr. Trump said it was probably making the deal at all, because everyone else is trying to take from the U.S.

Get Breaking News Delivered to Your Inbox

"I think my biggest concession would be making the deal," the president said.

The commander-in-chief mocked the "babies out there" who have bemoaned the tariffs he has engaged in with other nations. Some of those people have been members of Congress, Mr. Trump said, adding, "We wouldn't be here without tariffs."

The steel and aluminum tariffs, Mr. Trump said, will stay in place for the time being. Those tariffs are separate from the USMCA.

Late last night, our deadline, we reached a wonderful new Trade Deal with Canada, to be added into the deal already reached with Mexico. The new name will be The United States Mexico Canada Agreement, or USMCA. It is a great deal for all three countries, solves the many...... — Donald J. Trump (@realDonaldTrump) October 1, 2018

Mr. Trump declared the USMCA an "historic transaction!" Canadian Prime Minister Justin Trudeau meanwhile said it was a "good day for Canada & our closest trading partners." The warm reception of the deal comes after months of trade disputes between the two North American allies. Trudeau previously called the administration's tariff action against Canada "totally unacceptable" and "an affront to the longstanding security partnership between Canada and the United States."

White house economic adviser Larry Kudlow told reporters he isn't concerned about any lasting tensions between Canada and the U.S., after Mr. Trump has publicly criticized Canada and Trudeau over trade negotiations. Mr. Trump himself acknowledged that he had "very strong tensions" with Trudeau.

"There was a lot of tension, I will say ... it's all worked out," said Mr. Trump, who claimed that tension ended around midnight Sunday when the deal was reached.

But relationships with other nations on trade are unclear. Mr. Trump, who has declared the European Union one of the nation's greatest foes, gave few specifics on the future of that trade relationship.

"We'll see what happens. Who knows, I always say who knows. But we will see, I have a feeling we will be successful," Mr. Trump said.

The new trade agreement will need to be ratified by Congress — something that could be in jeopardy if Democrats take the House come November.

Kudlow did not express concern about what might happen if Democrats take control of the House — but Mr. Trump left room for doubt.

In his news conference, Mr. Trump said he didn't think Congress would be a problem — but then again, "anything you submit to Congress is trouble," he added.