European enthusiasm for President Barack Obama's ambitious programme of US renewal does not hide deep uncertainty over the likelihood of his delivering on measures to combat climate change.

Nine months from UN talks in Denmark, where world leaders will try to wrap up agreement on a new global climate change treaty to succeed the Kyoto Protocol that expires in 2012, there are real fears that events may conspire against Obama.

The depth of the disaster that has befallen the US economy in particular -- witness Friday's announcement of over 650,000 jobs lost in February alone -- and the difficulties Obama has faced getting Congress to greenlight his rescue plans underscore significant obstacles ahead.

Besides, given the US failure to meet its Kyoto commitments -- the protocol was signed by Bill Clinton's administration in 1997 but subsequently rejected by Senate -- European partners retain bitter memories of promises broken.

Several European environment ministers, including those from Denmark, France and Poland, this week met separately with the new team in charge of environment and climate issues for Obama's administration and numerous congressional representatives from both sides, Republican and Democratic.

UN climate chief Yvo de Boer, who was also in Washington for a first contact, restated the "encouragement" he has taken from Obama's stance.

Last month, de Boer described Obama's position on climate change as "a sea change" for the US, but this week, he too underlined the need to listen carefully to the views of Congress.

While Obama eventually got his 787-billion-dollar economic stimulus plan through Congress, battles still loom on healthcare, climate change, energy and education -- not to mention foreign policy.

"The lack of communication between the Senate and the administration around the time of Kyoto was an error we cannot allow to be repeated," de Boer said after this week's talks.

"It is necessary to pay very close attention to what Congress has to say" on the issue of Obama's proposed federal US law to introduce new caps, and subsequently reductions, on national carbon emissions, one of the principal battlegrounds come December's Copenhagen talks.

US emissions are the world's highest per capita, but Obama wants to see a 14 percent reduction from 2005 levels by 2020 and and an 83 percent drop by 2050.

Given the spectacular rise in global emissions and the distinct lack of action under the eight years of George W. Bush's administration, even this effort looks lightweight to some eyes -- but the challenges are, above all, political.

"The language is still as enthusiastic, but we sense a dampener with Congress, which could put the brakes on progress given (economic) difficulties," warned French minister Jean-Louis Borloo.

Observers doubt that Congress will have passed such a law by the time the Copenhagen crunch talks reach their conclusion.

In that event, then, what chance Washington being able to sign up to multilateral commitments in December?

For Denmark's climate minister, Connie Hedegaard, "it's up to the Americans to decide if they need to link the two or not."

She added: "The president and his administration have adopted a high profile on the issue and I don't want to speculate on what will happen if (the domestic law) doesn't work.

"We have to keep up the (international) pressure. Because, if we miss this opportunity, who can say if there will be another chance in 2010 or 2011?"

Carlos Pascual, vice-dDirector of the Brookings Institution, a respected Washington think-tank, says European partners need to be more "realistic."

"The pressures brought on by the state of the US economy are far greater than at the time of Kyoto. We have terrible problems here which we can't just ignore or leave to one side".

"First of all, we need to transform our economy."

With the next set of pre-Copenhagen negotiations scheduled for the end of March in Germany, de Boer stressed that Obama's team has "only been in place for five weeks."

"If the United States comes to Bonn with some basic principles and ideas, that will already be a strong step forward," he said.