Washington - European Union officials said Tuesday there had been a noticeable shift in climate policy since President Barack Obama took office, but said they expected much more drastic action before the United States can regain its international credibility.

After meeting US climate envoy Todd Stern in Washington this week, the EU's key environment ministers said it would be up to US legislators to improve the country's bargaining position by the time the world's climate officials meet to discuss a new global deal in Copenhagen in December.

"We've been waiting for eight years" for US action, said Martin Bursik, environment minister of the Czech Republic, which holds the EU's rotating presidency.

Bursik said the new administration had been moving with "double speed" to address global warming in a marked change from former president George W Bush, but much will depend on whether the US Congress follows suit.

Obama has said he wants to cut US greenhouse gas emissions blamed for global warming by about 15 per cent by 2020 and 80 per cent by 2050. But his signature policy - a cap-and-trade plan that would force US companies to pay for their emissions - faces significant opposition among US legislators who worry it will harm the economy.

Governments have set a deadline of December for agreeing on a new set of global targets to lower climate-damaging emissions. The EU ministers warned the deal could fall apart if the United States - the world's largest polluter together with China - could not show it had made significant progress by then in curbing its own emissions.

"The more the United States can deliver before Copenhagen, the more credibility the US will have," said Andreas Carlgren, Sweden's environment minister.

Stavros Dimas, the EU's commissioner for environment, said he expected at least the US House of Representatives to have approved a cap-and-trade bill by the Copenhagen summit, noting that developing countries like China and India were unlikely to cut their own emissions otherwise.

A vote in the House would send "a very powerful signal to the international negotiations and will help persuade our other international partners to come on board," Dimas said. (dpa)