WASHINGTON — President Trump said on Wednesday that he expects Iran to continue to comply with the terms of the 2015 deal that limits Tehran’s nuclear program, even as the United States violates it by reimposing what he called “among the strongest sanctions that we’ve ever put on a country.”

“I would advise Iran not to start their nuclear program,” Mr. Trump told reporters in a vague warning at the White House, a day after he withdrew the United States from the accord that was brokered between Iran and world powers.

Beyond betting that Iran’s leaders will return to the negotiating table, and seek a better deal, once they feel the sanctions’ bite, the president appeared to acknowledge that he has no Plan B for dealing with Tehran.

“Iran will come back and say, ‘We don’t want to negotiate,’” Mr. Trump told reporters. “And of course, they’re going to say that. And if I were in their position, I’d say that, too, for the first couple of months: ‘We’re not going to negotiate.’”