COPENHAGEN (NYT) – President Barack Obama will arrive here on Friday morning bent on applying a combination of muscle and personal charm to secure a climate change agreement involving nearly 200 countries.

He injects himself into a multilayered negotiation that has been far more chaotic and contentious than anticipated – frozen by long-standing divisions between rich and poor nations and a legacy of mistrust of the United States, which has long refused to accept any binding limits on its greenhouse gas emissions.

The world is looking to Obama to wrest some credible success from this process. And on Thursday, with almost 120 heads of state and government in attendance, there were some signs that a meaningful political deal might be at hand, including a slight shift in China’s position and a pledge by the United States to help the poorest nations cope financially with global warming.

But top negotiators here said that the talks could also prove a humiliating failure, because China and the United States, the world’s two largest emitters, remain deeply divided over a number of difficult problems.

Obama is putting a measure of his and the nation’s prestige on the line by entering a debate with so much still unresolved. It was only 11 weeks ago that he left this same city empty-handed after pleading for Chicago to be selected as site of the 2016 Olympics.

But the maneuvering and brinksmanship that has characterized the final week of the talks is also a sign of their seriousness – never before have global leaders come so close to a meaningful agreement to reduce the greenhouse gases linked to warming the planet.

The administration provided the talks with a palpable boost on Thursday when Secretary of State Hillary Rodham Clinton declared that the United States would contribute its share of $100 billion a year in long-term financing to help poor nations adapt to climate change.

Clinton’s offer came with two significant conditions. First, the 192 nations involved in the talks here must reach a comprehensive political agreement that takes effect immediately. Second, and more critically, all nations must agree to some form of verification – she repeatedly used the term “transparency” – to ensure they were meeting their environmental promises.