UN-hosted talks on climate change have ended in deadlock.
A US negotiator said the time was not right for negotiations
They were aimed at paving the way for the climate summit taking place in Bali in December which will focus on how to take forward the Kyoto Protocol.
However, the US said it was unlikely to take part in negotiations at the end of this year on a global agreement to cut emissions of carbon dioxide.
The UN acknowledged "sticking points", but said some issues had been resolved at the meeting.
United Nations Framework Convention on Climate Change (UNFCCC) Executive Secretary, Yvo de Boer, said: "We have come closer to broadening negotiations on a post-2012 regime by resolving some of the outstanding issues and clarifying which building blocks of a future agreement need to be put in place."
The Kyoto Protocol binds 35 nations to cut carbon emissions in a first phase until 2012. However, the main topic of discussion taking place in Bali later this year will be how to widen the deal to include the world's richest nations and the growing economies, such as the US, China, Brazil and India.
Experts say it is crucial that the talks go ahead as it will take several years to agree a deal to follow on from Kyoto.
However, Dr Harlan Watson, the United States' chief negotiator on climate, told the BBC: "I think there's a lot going on but I certainly wouldn't want to raise expectations, however, that there's going to be some sort of a new negotiation under the framework convention itself.
"I just think that it's not going to happen. It's certainly not something we think the time is right for."
Conservation group WWF criticised the meeting, saying that the "glacial speed" at which negotiations were taking place would not slow climate change.
"Two weeks of business-as-usual talks leave us wondering what it will take for governments to respond to the alarm bells," says Hans Verolme, director of the WWF Climate Change Programme.
The talks raise the spectre for more clashes at next month's G8 summit taking place in Germany.