International talks in Indonesia are entering their final day on Friday with delegates still sharply divided over terms for negotiating a new climate deal.
The U.N.'s top climate official, Yvo de Boer, says deadlock between American and European delegates is threatening to derail the talks.
Clashes center on whether to include mention of non-binding carbon emissions targets in a document due to be signed later today.
The so-called "roadmap" is meant to provide a framework for negotiating a new climate change treaty to replace the Kyoto Protocol.
At Thursday's session, former U.S. Vice President Al Gore said the United States is "principally responsible" for obstructing progress at the talks.
In Washington, the White House called Gore's comments "incorrect" and "not constructive."
The European Union has threatened to boycott global warming talks in the United States next month unless the Bali conference reaches agreement.