President Trump has long been clear that he would use tariffs as an economic sledgehammer against nations that refuse to bend to his demands.

He has been far less clear about what, exactly, those demands are — a strategy that allows him to declare victory when he sees fit.

Mr. Trump has said he wants Canada and Mexico to stop the flow of migrants at the border and curtail shipments of fentanyl. But at least publicly, he has offered only vague benchmarks to gauge their cooperation. Asked on Monday whether there was anything Prime Minister Justin Trudeau of Canada could offer to avoid tariffs, Mr. Trump said, “I don’t know.”

“We have big deficits with Canada like we do with all countries,” Mr. Trump said from the Oval Office. “I’d like to see Canada become our 51st state.”

In the end, Mr. Trump decided to postpone, for 30 days, the imposition of tariffs on Canada and Mexico, sidestepping a crisis that could have roiled the global economy. He suggested that he had wrenched concessions out of the United States’ neighbors, with Canada appointing a “fentanyl czar” and launching a joint strike force to combat organized crime and money laundering. Mexico, Mr. Trump said, promised to reinforce the U.S.-Mexico border with 10,000 members of its National Guard.

But it was not clear that any of those measures were major concessions. Mr. Trudeau, in a social media post, described actions that were already in progress under his country’s $1.3 billion border plan, including the deployment of additional technology and personnel to the border. Just a sliver of the total amount of fentanyl seizures occur at the U.S.-Canada border, according to federal data.