Barack Obama will be on hand for the final day of the two-week, 193-nation U.N. climate conference. But U.S.-China acrimony, a bitter divide between rich and poor nations and dissatisfaction with the U.S. emissions-reduction pledge clouded prospects for any agreement.

With global climate change talks at a critical stage, President Barack Obama flew to Copenhagen on Thursday to join more than 110 other world leaders looking to come up finally with an interim agreement.

Mr. Obama will be on hand for the final day of the two-week, 193-nation U.N. climate conference. But U.S.-China acrimony, a bitter divide between rich and poor nations and dissatisfaction with the U.S. emissions-reduction pledge clouded prospects for any agreement.

Sending presidents across the ocean to spend capital and time on an undetermined outcome is unusual. Schedules for foreign trips and international leader gatherings are usually set in advance in excruciating detail. Agreements are almost always inked ahead of time, with all but the signatures filled in.

Not so for this trip.

Not only was it unclear as Mr. Obama set off what the conference would produce, it was not certain how the president would spend his approximately nine hours there Friday. He was attending plenary sessions, and expected to hold some one-on-one sideline talks. But much of his time was purposely left fluid, and his brief remarks to the assembly were barely in draft stage before he left.

He does have a full schedule of meetings lined up with world leaders. He was meeting first with Danish Prime Minister Lars Loekke Rasmussen, the conference host. He also was to meet with Chinese Premier Wen Jiabao, whose country, like the United States, is a top carbon polluter. Others on the U.S. president’s schedule were President Luiz Inacio Lula da Silva of Brazil and Russian President Dmitry Medvedev.

This high-stakes jaunt is eerily similar to Mr. Obama’s first Copenhagen trip, when he unsuccessfully appealed for the 2016 Summer Olympics to be held in his adopted hometown of Chicago.

Then, he also arrived after an overnight flight from Washington and left later that day. The trip was more scripted, with a planned itinerary and presentation. But it carried no advance promise of good news, and produced none. Rio de Janeiro won the day.

Mr. Obama didn’t decide until late November to attend the climate talks. Doubt that he would go had increased after it became clear the conference would not produce a binding international climate treaty. Deemed too difficult a lift, leaders shifted the goal to producing a framework for a more formal agreement later.

Mr. Obama initially said he would stop in during the conference’s opening days. That way, his appearance would come on his own terms, with less hazard. But he abruptly changed his mind just before the conference started Dec. 7, deciding instead to go on the last day, when most other leaders would be there.

That decision was more consistent with Mr. Obama’s campaign promise to provide bold leadership on climate change. It also significantly increased the political risk.

Mr. Obama now is more vulnerable to being blamed for any failure. He could end the year with a glaring “incomplete” on yet another signature priority. He could make it even harder to pass hard-fought climate legislation precariously pending in Congress. He could be seen as weak if putting his prestige on the line fails to bring results {mdash} again.

“You go there to have conversation and sometimes awful things happen,” said Stephen Hess, a senior fellow emeritus at the Brookings Institution who has been a consultant, adviser and speechwriter to presidents dating back to Dwight D. Eisenhower. “It depends how often it happens, how it’s perceived by the press, the public and other nations, as well as the president’s enemies.”

Thursday’s offer from the U.S. to help raise $100 billion a year starting in 2020 to get poorer nations started on converting to clean energy and recovering from climate damage offered some hope. China responded by going some way to meet a firm U.S. demand that Beijing and other developing economies make cuts in emissions growth that are open to international verification.

But White House advisers still openly talked of the possibility the conference could end up a bust. “Coming back with an empty agreement would be far worse than coming back empty-handed,” presidential spokesman Robert Gibbs said Thursday. That kind of lowering of expectations could be an attempt to inoculate Mr. Obama from the fallout, or a negotiating ploy to scare recalcitrant nations into making moves of their own.

There has been much hope in Copenhagen that Mr. Obama would arrive with a new proposal and salvage the talks. That’s not likely.

For one thing, the U.S. emissions-reduction commitment purposely mirrors the legislation before Congress, which calls for 17 percent reduction in pollution from 2005 levels by 2020 -- the equivalent of 3 to 4 percent from 1990 levels and only a tiny fraction of offers from the European Union, Japan and Russia.

Even that target was hard-won in a skittish Congress, and Mr. Obama has decided he can’t go further without potentially souring final passage of the bill, approved in the House but not yet considered in the Senate. He also could imperil eventual Senate ratification of any global treaty that emerges next year.

Mr. Obama also will not be putting a specific dollar amount on Washington’s promised “fair share” contribution into a short-term, $10 billion-a-year fund for developing countries, said a White House official involved in the talks.

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