For three months, President Trump has been deeply engaged in the Iran conflict, planning the 38 days of attack, struggling to reopen the Strait of Hormuz and proclaiming “a whole civilization will die tonight,” then backing away to declare a cease-fire and a naval blockage of Iranian ports.

But on Monday, after days of haggling with Iranian officials through intermediaries on a preliminary agreement, Mr. Trump declared it was starting “to get very boring.”

“I don’t care if they’re over, honestly,” he told Eamon Javers of CNBC when asked about reports that the Iranians, angry at continued Israeli strikes in Lebanon and low-level conflict with the United States in the Persian Gulf, were threatening to stop negotiating. “I really don’t care. I couldn’t care less. If they’re over, they’re over.”

There are reasons to doubt that Mr. Trump is truly so unconcerned: Gasoline prices have soared since the war began, with a senior Exxon-Mobil official predicting recently that prices could go far higher, and Republicans are taking note of how deeply unpopular the war with Iran is with their constituents. In recent weeks he has professed indifference about a range of issues that carry deep political consequences for him, including the midterm elections and the financial situation that Americans are facing.

But even for Mr. Trump, who has veered from threatening the Iranians with annihilation to declaring that they had already agreed to American terms to fuming that they have not, it seemed strange that he thought the whole conflict was becoming a bore.

After all, just hours before he had written in a social media post that negotiations were “continuing, at a rapid pace, with the Islamic Republic of Iran.” There were widespread reports that on Friday he toughened the requirements on a preliminary accord with Iran — one that would just set up another, deeper negotiation — because he was concerned about provisions for returning frozen funds to the Iranian government and over who would handle the recovery of Iran’s highly-enriched uranium.

These were details, but vitally important.

Back in March, Mr. Trump confidently predicted the conflict would be over in a few weeks, saying it was not possible to suffer from boredom while facing off against a longtime American adversary: “Somebody said today, they said, ‘oh, well, the president wants to do it really quickly. After that, he’ll get bored.’”

“There’s nothing boring about this,” he added.