WASHINGTON (Reuters) - U.S. flexibility in negotiating a global warming pact depends on passing a law to cut greenhouse gas emissions, which is not an insurmountable task, Washington's top climate envoy said on Thursday.
"We are going to fundamentally be guided by what happens in our own legislative process," Todd Stern, the U.S. Special Envoy for Climate Change, told Reuters in an interview when asked whether there was room for maneuver in the U.S. stance at U.N. climate talks.
President Barack Obama wants to cut U.S. emissions by roughly 15 percent by 2020 -- back to 1990 levels -- mostly through a cap-and-trade system that limits how much carbon dioxide and other greenhouse gases big factories can emit.
That system is the crux of a bill that the U.S. Congress is now studying. The measure faces its toughest hurdle in the 100-member Senate, where 60 votes are needed for passage, but Stern said he thought it would be possible to get enough support to pass the bill.
"I don't think the problem's too insurmountable," he said.
Stern said the cap-and-trade portion of the bill was not the only way to cut U.S. emissions.
"There may be other things that contribute to emissions reductions in the United States that aren't part of that ... bill," he said.
Stern said the major developing countries -- such as fast-growing China and India -- would have to play a big part in fighting global warming for the world to succeed in tackling the problem. But he declined to give the U.S. position on how far such countries needed to go.
"The major developing countries need to do significant things, need to make real commitments," he said. "There is no other way to solve this problem."
Picking out one country in particular, Stern said China was doing a great deal to fight climate change but had to do more, adding that its greenhouse gas emissions were "huge and at an unsustainable level."
Editing by John O'Callaghan