Legalities aside, the fact that President Trump is indicating that the tariffs will be negotiable on a country-by-country basis, rather than set in stone, diminishes the risk that this will be the beginning of an all-out trade war in which the very underpinnings of global commerce are threatened.

“Countries are going to be happy — we’re going to show great flexibility,” Mr. Trump said Thursday, which is something of a contrast with his Twitter message last weekend arguing that trade wars were “good, and easy to win.”

The mix of bluster and openness to compromise is consistent with a longstanding pattern that was evident in President Trump’s business career. Still, the stakes here are the global economy rather than a real estate deal, which leaves experts in the field unnerved.

“As is so often the case, President Trump starts out with extreme positions, then often tends to modify them somewhat as time goes on,” said Marina v.N. Whitman, a professor of business and public policy at the University of Michigan. “But given the importance of these relationships between allies, even these little pokes and tit-for-tat disputes is pretty disturbing.”

It is certainly possible for this to spiral into a broader trade conflict that involves higher tariffs on all sorts of goods and services and an unraveling of the trade arrangements built over decades.

But the pattern so far in the Trump administration has been one in which the president stakes out a bold, aggressive position, only to compromise as the lawyers and economists in his administration fill in the policy details.

That raises the possibility of an extended period of global tension regarding trade, with occasional flare-ups over tariffs or other restrictions on individual products, but not the kind of trade war that occurred in the 1930s as nations competed to block themselves off from imports. Or, as Terry Haines, managing director of Evercore ISI, calls it, “no trade war, but also no trade peace.”