The U.S., the only industrial nation to reject a 1997 climate agreement struck in Kyoto, initially opposed efforts to strike a deal in Bali. But the American delegation reversed itself after representatives from tiny Papua New Guinea demanded the U.S. lead or get out of the way.

“Miraculously, I was able to save this one, but I didn’t know why,” Ban said.

Ban said he discovered the reason at a White House dinner in the final days of Bush’s presidency, when the 43rd president told the U.N. leader about his instructions to his team of negotiators when the talks were deadlocked.

He said Bush told him: “Suddenly, you came to my mind. Then I told the delegation head, ‘Do what the secretary-general of the U.N. wants to do.’ ”

Paula Dobriansky, the U.S. leader at the talks, said at the time she changed her mind because of pleas from smaller countries and not instructions from Washington, according to Reuters.