FACTBOX: How much might U.S. pledge in climate aid?

The EU has promised around $3.5 billion a year for three years as its contribution to a start-up fund that could eventually grow to $100 billion or more annually.

The Obama administration says it will do its fair share, but has not yet promised anything for the next three years or beyond. The United States this year will contribute about $1.2 billion.

President Barack Obama says fighting climate change is one of his top priorities and some Democrats in Congress want him to back that up with $3 billion next year for poor country financing. Any promise of money could face tough opposition from Republicans in Washington, many of whom also oppose government mandating carbon pollution reductions.

To put $3 billion of U.S. spending in perspective, here are some other programs Washington has funded recently or wants to fund:

-- Around $630 billion for military programs next year, including around $128 billion for the wars in Iraq and Afghanistan. Total war funding since 2001 is approaching $1 trillion;

-- $3 billion was spent to help U.S. consumers scrap their old cars and buy new, more fuel efficient ones this year. The program also was a boost to the ailing U.S. auto industry;

-- Nearly $4 billion might be spent next year on 5,224 small projects important to individual lawmakers' states or congressional districts. Senator John McCain has complained that one of those projects would fund University of Nebraska research into surgical operations in outer space;

-- With U.S. government debt rapidly rising, Congress wants to expand the federal government's borrowing authority by $1.8 trillion. The current debt is about $12.1 trillion.