The inability of the US to commit to reducing greenhouse emissions has long been cited as a reason behind the stalemate of global climate talks.
And any faint hopes for success at top-level international climate-change negotiations in Cancun were dimmed when Barack Obama's Democratic party lost ground to conservatives in US mid-term elections.
The US, one of the two major carbon polluters, has yet to commit to legal targets that would reduce greenhouse emissions.
Negotiators at the convention that begins this week now aspire to achieve nothing greater than agreement on technical issues, such as how to account for emissions in developing nations.
"Climate change is a particularly challenging issue as it must be handled at the global level," said Professor Daniel Esty, who teaches at the Yale Law School and the Yale School of Forestry & Environmental Studies. "No country can solve the problem on its own.
"The US is not in a position to negotiate a final treaty because it lacks a federal position on the issue."
The American president has been working on a climate change and energy bill stipulating some cuts. But with the rival Republican party gaining control of the US House of Representatives, the chances of this bill becoming law are slim, he said.
"We have a divided situation now," said Prof Esty, who advised the Obama campaign on energy and environmental issues in 2007 and 2008. "The Republican leadership in the Senate and the House have indicated they are not willing to work with the president."
Dr Anna Korppoo, the programme director at the Helsinki-based Finnish Institute of International Affairs, said the situation dramatically lessened any chance for a breakthrough in Cancun.
"Now it is clear President Obama will not get any climate change legislation through," she said. "It is impossible to come up with anything significant."
The difficulty, she said, is that all players have been expecting concessions from other parties in order to commit themselves.
Discussions in Cancun are to be divided into two main tracks. One seeks to redefine responsibilities under the Kyoto Protocol, an agreement that obliges 37 industrialised countries to reduce greenhouse emissions by five per cent on 1990 levels in the period between 2008 and 2012.
The Cancun convention track will focus on the US, which did not ratify the Kyoto Protocol, and examine the responsibilities of developing nations.
One of the key countries in the negotiations is China, which is considered the world's other major polluting country. As a developing nation, China is not obliged to commit to any legal emissions cuts. However, some industrial countries have demanded that China make concessions before they commit themselves to any deeper reductions.
Prof Esty said the lack of a federal US position represents a missed opportunity. Had America been able to come with anything concrete at the negotiating table, China could have committed as well, he said.