U.N. climate talks were thrown into disarray Monday as developing countries blocked negotiations, demanding that rich countries raise their pledges for reducing greenhouse gas emissions.

Representatives from developing countries said they refused to participate in any working groups at the 192-nation summit until the issue was resolved.

The move was a setback for the Copenhagen talks, which were already faltering over long-running disputes between rich and poor nations over emissions cuts and financing for developing countries to deal with climate change.

"Nothing is happening at this moment," Zia Hoque Mukta, a delegate from Bangladesh, told The Associated Press. He said developing countries have demanded that conference president Connie Hedegaard bring the industrial nations' emissions targets to the top of the agenda before talks can resume.

Earlier Monday, British Climate Change Secretary Ed Miliband said it's up to him and his counterparts in Copenhagen to help bridge that gap between rich and poor countries and "not to leave everything" to the 100 world leaders _ including President Barack Obama _ who start arriving Wednesday.

"There are still difficult issues of process and substance that we have to overcome in the coming days," Miliband said. "Can we get the emission cuts we need? We need higher ambition from others and we will be pushing for that."