When British Prime Minister Theresa May told Trump by phone that British authorities were 95 percent sure that Moscow was responsible, Trump replied, “Maybe we should get to 98 percent.”

During a weekend retreat at his Mar-a-Lago estate, Trump’s advisers persuaded him to support a plan to expel 60 suspected Russian intelligence operatives from the United States, telling him that Washington’s move would be matched in magnitude by allies in Europe.

Trump acquiesced, but his commitment unraveled on the trip back to Washington.

“Maybe we shouldn’t do this,” he said to deputy national security adviser Ricky L. Waddell during the short helicopter flight from Andrews Air Force Base to the White House on March 25.

The expulsions were set to be announced the next day in coordination with allies in Europe — an international show of resolve — and Trump was balking. Late that evening, Waddell scrambled to pull together a Situation Room meeting to confer with other top advisers on how to salvage the plan. White House Chief of Staff John F. Kelly, who called in on a secure phone line, said that he would phone Trump at his residence. “I’ll convince him,” Kelly said.

Kelly succeeded. But when the expulsions were announced, Trump erupted. He had expected France, Germany and other countries each to match the U.S. total, rather than for the cumulative response from Europe to be roughly equal to that of the United States. Trump worried that Putin would see him as the aggressor and accused aides of misleading him.

“There were curse words,” one official said, “a lot of curse words.”