A warning to delegates in Copenhagen: If you're looking for President Barack Obama to cave to pressure and deepen U.S. efforts to curb greenhouse gases, don't bet on it.
Mr. Obama, like most world leaders, is constrained by tough politics at home. And that makes it tougher for the summit to produce meaningful pollution cuts.
U.S. officials stressed Wednesday that when Mr. Obama travels to the climate conference in Denmark this week he won't bring anything to the talks beyond Washington's already stated goals: to commit to reducing greenhouse gases by 17 percent from 2005 levels by 2020 and to pay a "fair share" into a $10 billion fund to help developing countries deal with climate change.
Developing countries have called on the United States and Europe, which are responsible for most of the greenhouse gases that have gone into the atmosphere in past years, to make much deeper cuts in the short term - by at least 34 percent from 2005 emission levels by 2020. Those are reductions far beyond what members of Congress - even those supporting climate legislation - say they will accept.
"We don't want to promise something we don't have," Todd Stern, chief of the U.S. delegation to the climate conference, told reporters this week in Copenhagen. He said he did not anticipate any change in the U.S. commitment.
Said Rep. Edward Markey, D-Mass., a co-author of a climate bill already passed by the House: The president "is not going to go further. ... The words he is going to use are the same words he has been using for the last two weeks."
White House press secretary Robert Gibbs, too, kept a tight hold on expectations for the summit. Noting that there are remaining disagreements among delegates, he said the president "is hopeful that his presence can help" produce "a strong operational agreement, even as we work toward something even stronger in the future."
For Mr. Obama, it's something of a juggling act: On the one hand he wants to present a strong case to the world that after eight years of relative inaction by the Bush administration, the United States is ready to tackle the climate issue head-on, but he is also fully aware of the political and economic realities back home.
Stern and other administration officials have said frequently they do not want to repeat the mistake of Kyoto, where the United States was key in hammering out a climate accord, only to see President Bill Clinton decline to submit it to the Senate for ratification for fear of it being rejected. Later it was discarded altogether by President George W. Bush.
Any emissions reduction targets - and commitments to financing - will have to be backed up by a Congress that is skittish about passing new mandates for heat-trapping gases in the midst of a recession and is concerned that other countries that don't follow suit will outcompete the U.S. in a global marketplace.
But Mr. Obama is not alone in facing conflicting domestic and international priorities.
China has refused to even discuss actually reducing its current greenhouse gas pollution because that would go contrary to the country's rapid pace of economic growth. It says it will cut emissions as a percentage of future economic growth but has balked at international verification and monitoring, calling that a threat to its sovereignty. Instead it prefers to act as its own watchdog on compliance.
Likewise, India, wanting to protect its future economic growth, announced it would commit only to slowing the growth of its greenhouse emissions and not accept a legally binding target.
Mr. Obama has said his commitment at Copenhagen would mirror legislation already before Congress, calling for 17 percent reduction in pollution by 2020 and 80 percent by mid-century. But even that target has been denounced by Republicans as a "jobs killer" that would lead to higher energy costs. Democrats from states with energy-intensive industries are complaining, too.
Opinion polls have shown people have limits on how much they want to pay to solve the problem.
A recent AP-Stanford University poll revealed that while three-quarters of respondents said they support action to address climate change, just as many said they would oppose the plans considered by Congress and backed by Mr. Obama if they raised their electricity bills by $25 a month. A majority - 59 percent - wouldn't support any action if it meant electricity would cost $10 more.
Even Democrats who support climate legislation have warned the White House against committing to something at Copenhagen that Congress can't deliver - while some Republican lawmakers have urged Mr. Obama to reject mandatory emission cuts altogether.
In Copenhagen, Stern, the U.S. delegation head, declared: "Our commitment is tied to our anticipated legislation. We don't want to promise something we don't have."
At the same time, administration officials said - and are arguing in meetings in Copenhagen - that the U.S. is doing more to reduce the climate change threat than getting legislation passed by Congress.
In recent days, the White House has choreographed a series of announcements and events in Washington designed to highlight those efforts - from tax breaks for renewable energy manufacturers to the president visiting a home remodeling store to declare it is "sexy" to better insulate your home.
The White House distributed a memo noting that the economic recovery program contains $80 billion to help promote clean energy development including money for renewable energy projects, nuclear power plants, more fuel efficient motor vehicles and commercial development of carbon capture technologies to be used at coal burning power plants.
It was a message designed for both Copenhagen and domestic consumption.