President Obama, speaking to world leaders gathered here at the frenzied end of two weeks of climate talks, urged them to come to an agreement — no matter how imperfect 。

Mr. Obama met privately with China’s prime minister, Wen Jiabao, in an hourlong session that a White House official described as “constructive.”

However, in a day of high brinkmanship and seesawing expectations, Mr. Wen did not attend two smaller, impromptu meetings that Mr. Obama and United States officials conducted with the leaders of other world powers, an apparent snub that infuriated administration officials and their European counterparts and added more uncertainty to the proceedings.

At 7 p.m. Copenhagen time, Mr. Obama and Mr. Wen met again, joined by Prime Minister Mammoghan Singh of India and President Luiz Inácio Lula da Silva of Brazil.