COPENHAGEN - As President Obama prepared to visit the historic climate conference here, there were signs Wednesday of a break in the impasse between rich and developing nations.

The United States and Japan agreed to make major contributions to the developing world to keep a deal alive. And the leader of a bloc of African nations said they would accept a smaller -- though still sizable -- package of financial aid in return for going along with an agreement.

But tear gas hung in the air outside the conference center as protesters demanding faster and more stringent cuts in greenhouse-gas emissions clashed with police. And inside, talks were slowed by disagreements within the developing world -- which has proved an unexpectedly powerful and fractious force.

Clinton in Copenhagen today

Secretary of State Hillary Rodham Clinton was on her way to Copenhagen as negotiations over a draft agreement effectively came to a halt after an all-night session that broke up at dawn Wednesday.

Some environmentalists expressed hope that Obama's appearance Friday, the final day of the 12-day talks, could help conclude these chaotic weeks with a global deal.

"If the pieces are here, President Obama is the only person who can pull them together into an agreement," said Fred Krupp, president of the Environmental Defense Fund. "We expect him to do so."

British Climate Change Secretary Ed Miliband told the BBC the climate change talks were "certainly on a knife edge and in real grave danger. ... It now needs leaders, unfortunately, to come in and move this process forward."

The U.S. delegation objected to a proposed text it felt might bind Washington prematurely to reducing greenhouse gas emissions before Congress acts on the required legislation.

Veterans of these conferences said such stalls were not unusual. "I know that often negotiations reach the halfway point about an hour before an agreement," said Jennifer Haverkamp, a former trade negotiator and a climate analyst for the Environmental Defense Fund.

A key concession

In a moment that distilled the diplomatic dance in Copenhagen, Ethiopian Prime Minister Meles Zenawi -- who is representing all of Africa here -- unveiled his proposal Wednesday for a system in which rich countries would provide money to poor ones to help deal with the effects of climate change. These effects might include rising sea levels, droughts and changing rainfall patterns.

Zenawi said he would accept $30 billion a year in the short term, rising to $100 billion a year by 2020, for poor countries worldwide. This was seen as a key concession by developing countries, who previously spurned that figure -- originally proposed by European countries -- as too low.

Also Wednesday, Japanese officials said their country would provide $15 billion over the next three years to help poor nations adapt to climate change and lower emissions. But that offer would be good, State Secretary for Foreign Affairs Tetsuro Fukuyama said, only if a global agreement is reached this week.

Among Clinton's first scheduled meetings Thursday is a private talk with China, America's protagonist in a dispute over whether developing countries must report and verify their actions to reduce emissions.

By JULIET EILPERIN and DAVID A. FAHRENTHOLD, Minneapolis Star Tribune, December 16, 2009