Prime Minister Fredrik Reinfeldt of Sweden, which holds the rotating EU presidency, said the emissions bill being debated by a key US Senate committee was "going in the right direction" but was "not as lengthy as we would hope."

Members of Congress are debating a bill aimed at reducing greenhouse gas emissions in the United States, which many see as a prerequisite to a deal at an upcoming UN summit in Copenhagen aimed at replacing the Kyoto Protocol.

Earlier in the week US Republican lawmakers boycotted a committee meeting on the bill -- backed by President Barack Obama -- which some see as a sign of non-commitment that could stall negotiations already deadlocked over help for developing countries to fight global warming.

Reinfeldt voiced uncertainty about whether the legislation would be ready before the December 7-18 UN summit, but said US input was important given its historical responsibility as a major polluter.

"We can't have the number one causer of this problem... outside of the deal," Reinfeldt said.

He said he was hoping for a "strong agreement" in Copenhagen, but downplayed expectations about a solution to the contentious issue of legally binding emission cuts.

"What we hear is that the kind of legally binding agreement that we for instance did inside the EU will probably not be possible," said Reinfeldt.

"Some of the countries like the US say we do not have the support in our Congress to make ratification."

Reinfeldt was speaking to reporters in New Delhi, where he was taking part in the annual India-EU summit.

Acknowledging that the industrialised world had failed to follow a sustainable model of living, Reinfeldt urged poor nations to avoid a high-polluting path to modernisation.

"We are very interested to see that countries like India and China do not do the same mistakes all over again," he said.