UNITED NATIONS — Gary D. Cohn, the top White House economic adviser, told ministers from several major allies on Monday that the Trump administration was “unambiguous” about its plans to withdraw from the Paris agreement on climate change unless new terms were met.

Ministers emerging from the 90-minute breakfast in a back room of The Smith, a brasserie near the United Nations, described the meeting as genial and productive. But, they said, they learned no specifics from Mr. Cohn about the likelihood of the United States’ remaining in the global accord or what changes would be needed to make it acceptable to the White House.

“I made the president’s position unambiguous, to where the president stands and where the administration stands on Paris,” Mr. Cohn told reporters after the meeting. “We reaffirmed the president’s statement that he made in the Rose Garden, and we continue to reinforce what the president is saying.”