BANGKOK, Thailand - The honeymoon appears to be over for the United States at UN climate talks.

After being applauded for re-engaging in negotiations this year, the American delegation at talks in Bangkok this week has found itself at times portrayed much as its Bush administration predecessors were -- as villains who aren't interested in reaching an ambitious global warming treaty when leaders from 120 countries meet in Copenhagen in December.

The deal would replace the Kyoto Protocol, which expires in 2012.

The delegation hasn't brought much to the table -- partly because climate change legislation hasn't passed the U.S. Congress -- while angering some developing countries by insisting they must show proof they are taking action to reduce heat-trapping emissions.

"We must attack this problem with a sense of urgency and ambition and quite frankly we are not seeing the level of urgency and ambition from the U.S.," said Selwin Hart, a delegate from Barbados who was speaking for the Alliance of Small Island States, who fear they'll be swamped by rising seas caused by global warming. "This process will go nowhere if we don't see leadership from the U.S."

Lumumba Di-Aping, chairman of the developing block of nations known as the G-77 and China, went further Thursday, accusing the Americans of drawing up climate legislation that advances their "own national interest" without regard for the rest of the world.

On Wednesday, the U.S. Senate introduced a climate bill that calls for a 20 per cent cut in 2005 levels by 2020 in greenhouse gases blamed for global warming. That's a deeper cut than the House passed earlier or what President Barack Obama wants, but it still falls short of the emission reductions many scientists say are necessary.

"We need real, aggressive reduction target commitments that say this is something worse than Sept. 11," Di-Aping said, referring to the terrorist attacks in the U.S. in 2001.

The American delegation has insisted it wants a deal in Copenhagen to cap greenhouse gas emissions and has been praised by delegates for being much more engaged in the talks than its predecessors in the Bush administration.

Still, it has managed to irritate India and other major developing countries by insisting that they agree to take part in a system that monitors and verifies actions promised in any new agreement.

"We expect them to stand behind those actions the way we would stand behind ours and reflect them in this international agreement with a willingness to be transparent about them, to enable third parties to review them, and be committed to those efforts," said Jonathan Pershing, the chief U.S. negotiator.

Delegates to the two weeks of talks in Bangkok have said negotiations are too slow, partly due to the lack of a clear signal from the United States on what actions it will take.

Developing countries will be reluctant to join a treaty without firm commitments by the United States, which until recently was the world's largest emitter of greenhouse gases but is now second to China. Pershing has acknowledged it would be difficult for the U.S. to extract concessions from other countries without a climate law, which he said was unlikely to be ready before Copenhagen.

The United States rejected the 1997 Kyoto Protocol because it exempted such countries as India and China, both major polluters, from obligations. The Obama administration is determined that a replacement pact must require developing countries to cut emissions.

Most countries have agreed that any new pact should include provisions to maintain temperature increases of two degrees Celsius below preindustrial levels of about 150 years ago. That would require emissions cuts from industrial countries of 25 per cent to 40 per cent below 1990 levels by 2020, far above the 15 to 23 per cent cuts rich countries have offered so far.