The 10-day-old climate talks ran into disputes and paralysis as they entered a critical stage Wednesday, just two days before President Barack Obama and more than 100 other national leaders hope to sign a historic agreement to fight global warming.

Poorer nations stalled the talks in resistance to what they saw as efforts by the rich to impose decisions falling short of strong commitments to reduce greenhouse gases and to help those countries hurt by climate change. Conference observers said, however, that negotiators still had time to reach agreements.

Outside the meeting site in Copenhagen's suburbs, police fired pepper spray and beat protesters with batons as hundreds of demonstrators sought to disrupt the 193-nation conference, the latest action in days of demonstrations to demand "climate justice" _ firm steps to combat global warming. Police said 260 protesters were detained.

Earlier, behind closed doors, negotiators dealing with core issues debated until just before dawn without setting new goals for reducing greenhouse gas emissions or for financing poorer countries' efforts to cope with coming climate change, key elements of any deal.

"I regret to report we have been unable to reach agreement," John Ashe of Antigua, chairman of one negotiating group, told the conference.

In those talks, the American delegation apparently objected to a proposed text it felt might bind the United States prematurely to reducing greenhouse gas emissions before Congress acts on the required legislation. U.S. envoys insisted, for example, on replacing the word "shall" with the conditional "should."

Later, faced with complaints from developing nations about such changes, the Danish leaders of the talks crafted what they hoped would be a compromise text. Even before that was circulated, however, the unhappy nations _ the Group of 77 and China _ met separately to decide on a position.

"They are unhappy about these texts being handed to them from above," an African delegate said outside the meeting, speaking on condition of anonymity because he was not authorized to talk to the media.

The latest dispute highlighted the undercurrent of distrust developing nations have for the richer countries in the long-running climate talks. But veteran observers said it was too early to give up on the talks, which are supposed to end Friday with Obama and the other leaders approving a final agreement.

"A lot of things are in play," said Fred Krupp of the U.S. Environmental Defense Fund. "This is the normal rhythm of international negotiations."

Venezuelan President Hugo Chavez echoed the protesters' sentiments when he told the assembly: "If the climate was a bank, a capitalist bank, they would have saved it."