The U.S. government insists it's deeply engaged in talks started this week on the world's next climate pact, but other negotiators are already looking ahead to the next administration - and wondering what to expect.

Nations have less than two years to piece together a deal that scientists say is needed to cut emissions of greenhouse gases and stop the planet's temperatures from rising so high they trigger an environmental disaster.

The high-stakes negotiations that began Monday in Thailand, however, are complicated by the coming presidential election in the United States.

Crucial details - such as how much Washington is willing to cut its emissions - can't be fully discussed until a new president takes office next year, slowing action on a final deal, some negotiators say. And it's far from certain what a new administration's negotiating stance will be.

"The nature of the U.S.' commitment ... is unclear, and I suspect we're not going to get a clear signal from the U.S. until after the next election," said Ian Fry, a representative for the island nation of Tuvalu, which faces danger from rising sea-levels caused by global warming.

"The uncertainty is troubling, particularly for highly vulnerable countries, like small island states," he added.

The world's nations agreed in a massive conference in Bali late last year to conclude a pact by December 2009. The agreement would succeed the first phase of the Kyoto Protocol warming agreement, which expires in 2012.

President Bush has rejected the 1997 Kyoto global warming pact, arguing it would hurt the economy and was unfair because developing countries weren't required to cut emissions. The agreement committed 37 wealthy nations to cut greenhouse gas emissions an average of 5 percent below 1990 levels by 2012.

Harlan Watson, the head of the U.S. delegation in Bangkok, insisted the administration was fully involved in the negotiations for the new pact.

Congress and leading U.S. presidential candidates have shown a willingness to cap emissions. But Watson said the U.S. still wants commitments from major developing nations as well, no matter who is in the White House.

So far at Bangkok, however, he has limited his public statements to procedural issues.

"At this point in the process, there's no enthusiasm for talking" about specific targets, he said. Later he added: "We don't want to do anything that's going to cut off the next administration's options."

U.N. climate chief Yvo de Boer acknowledged that one of the toughest parts of the haggling ahead - on how much industrialized countries will cut their gas emissions - would best be discussed with a new U.S. administration.

The final goal of the talks will be a complex document to include emissions reduction commitments by industrialized countries, measures by developing countries, and financing and technology transfer to help them control emissions and adapt to the effects of rising temperatures.

The United States, as the world's largest economy and one of two leading emitters with China, is a major player. Negotiators agree any new pact is doomed unless Washington joins.