But now, the well is running dry. 

The secretary of state's offer to spend tens of billions of dollars over the next several decades is being met with strong resistance back in Washington. 

Republicans wielding power next year will have no appetite to spend discretionary money on climate-related issues, especially when they doubt the underlying science. And the demise of comprehensive climate legislation leaves the administration without the long-term funding stream it had envisioned using to cover much of its pledge. 

Obama administration officials insist they are full-steam ahead with their pledge to help create a $30 billion short-term fund to help developing countries keep their forests standing, gain access to low-carbon energy technologies and adapt to rising seas, extreme weather and new crop patterns. 

To pay its share, the United States will triple its financial contributions in fiscal year 2010 on climate-related activities to $1.7 billion, including $1.3 billion appropriated from Congress and an additional $400 million in development finance and export credits that don't need approval from Capitol Hill. 

Obama also has asked Congress for $1.9 billion more in fiscal 2011, though that appears unlikely as lawmakers prepare a continuing resolution for the remainder of the 2010 budget. 

"They can make all the promises they want; they may have to find somewhere else to pay for it other than the Appropriations Committee," said Sen. Patrick Leahy (D-Vt.), chairman of the spending subpanel that oversees the State Department's budget. 

"They promised to pass a cap-and-trade bill and reminded us they wanted to give away $100 billion, and I said, 'From where?'" incoming House Energy and Commerce Committee Chairman Fred Upton (R-Mich.) told POLITICO. 

Republican Sens. Jim Inhofe (Okla.), David Vitter (La.), John Barrasso (Wyo.) and George Voinovich (Ohio) urged Clinton last week to freeze all future spending requests related to international climate change finance programs and make no new commitments. 

"You're looking at a thing where you have a lot of people in Congress who are suspicious of foreign assistance,” said Mark Helmke, spokesman for Senate Foreign Relations Committee ranking member Dick Lugar (R-Ind.). "All of a sudden, we're putting a whole lot of new demands at a time when people want to cut spending and when people are getting tired of money going overseas when we have a lot of concerns domestically." 

State Department spokesman Ben Kobren said the administration remains committed to funding its share of a $100 billion package that Clinton helped announce last year in Copenhagen — even though a good chunk of the U.S. funds were envisioned to come from auctioning credits in a cap-and-trade system. 

Kobren said the fund will be filled by the world's richest nations through both public and private financing.

But the lack of domestic support means the United States' position in the Cancun, Mexico, talks scheduled to end Friday isn't terribly strong. 

"As a general matter, the United States is in a difficult position in this negotiation on the finance and the mitigation commitment side with the lack of developments on the Hill," Jennifer Haverkamp, an international trade expert at the Environmental Defense Fund, said from Mexico. 

"They have very little to put on the table," she added. 

Kobren said funds from the $100 billion account wouldn't be distributed unless developing countries agree to make their own "meaningful mitigation actions" that are open to transparent accounting methods. Negotiators in Cancun are haggling over exactly that issue, and the talks are expected to remain at an impasse beyond this week’s summit as rich and poor nations define what exactly is an appropriate inspection method for a country’s emission reduction policies. 

Environmentalists say the Obama administration can still overcome the domestic budgetary concerns by relying on public-private financing and multilateral institutions for both its short- and long-term commitments. One of the best ways to do that is to tout the ancillary benefits that come from spreading small sums of money around the world, helping poor countries that are strategic U.S. allies in fighting terrorism and economic recovery. 

"If you approach this just as a climate question, given the newly elected members particularly on the Republican side, we will I think run into some skepticism," said John Podesta, president of the Center for American Progress and a former White House chief of staff to Bill Clinton. 

Podesta's group joined Al Gore's Alliance for Climate Protection earlier this week in calling for the U.S. to offer $10 billion through public financing by 2015, as well as a series of bilateral climate partnerships costing about $500 million apiece with key allies like Indonesia and India. The groups also suggested the United States take the lead in an effort to increase multilateral development banks' lending to about $20 billion per year by 2015 for renewables and energy efficiency projects. 

The left-leaning groups also called for between $60 billion and $160 billion in private financing by 2015. And for those that have cap-and-trade programs, like the European Union, the report suggested allotting about $20 billion per year by 2015. 

"It's going to be a challenge for governments to put forward the kinds of public funding contemplated even a year ago in Copenhagen," said Kathleen Frangione, former top climate staffer to Sen. John Kerry (D-Mass.), author of the unsuccessful Senate cap-and-trade bill. "Being honest about it, the political winds make it perhaps more challenging than we might have expected."