BALI, Indonesia - European nations threatened yesterday to boycott U.S.-sponsored climate talks next month unless the Bush administration compromises and agrees to a "road map" for reducing greenhouse gases blamed for global warming.

With the U.N. climate conference in its final hours, Nobel laureate Al Gore said the United States was "principally responsible" for blocking progress toward an agreement on launching negotiations to replace the Kyoto Protocol when it expires in 2012.

He urged delegations to reach the required unanimous agreement before the conference's scheduled end today - even if it meant putting aside goals for emissions cuts.

"You can do one of two things here," the former vice president said. "You can feel anger and frustration and direct it at the United States of America, or you can make a second choice. You can decide to move forward and do all of the difficult work that needs to be done."

The United States, Japan, Russia and several other governments refused to accept language in a draft document suggesting rich nations consider cutting emissions 25 to 40 percent by 2020, saying specific targets would limit the scope of future talks.

European nations and others argued that numerical goals would be essential reference points in efforts to curb global warming.

All sides agree it is impossible to deal with climate change unless the United States is involved. It is the world's leading emitter of carbon dioxide and other greenhouse gases and the only major industrial country that did not ratify the Kyoto Protocol.

President Bush views his own climate talks as the main vehicle for determining action by the United States - and, he hopes, by other nations. The Jan. 30-31 session in Honolulu is a continuation of September talks at the White House known as the Major Economies Meeting on Energy Security and Climate Change.

The United States has invited 16 major nations - including European countries, Japan, China and India - to discuss a program of what are expected to be nationally determined, voluntary cutbacks in greenhouse gas emissions.

But the European Union warned of a boycott unless Bush drops his opposition to mandatory cuts.

"No result in Bali means no Major Economies Meeting," said Sigmar Gabriel, the top EU environmental official.

The main goal in Bali is to set up two years of intense dialogue about how to slow global warming and head off predictions of rising sea levels and worsening floods and droughts.

Yvo de Boer, the U.N. climate chief, said he was worried that the U.S.-EU deadlock could derail any consensus in Bali on how to proceed.

"If we don't get wording on the future, then the whole house of cards falls to pieces," he said.

The U.S. delegation said that while it continued to reject inclusion of specific emission-cut targets, it hoped eventually to reach an agreement that would be "environmentally effective" and "economically sustainable."

"We don't have to resolve all these issues . . . here in Bali," said Undersecretary of State Paula Dobriansky, head of the U.S. delegation.

Appearing at the U.N. conference four days after receiving the Nobel Peace Prize for his work on alerting people to the threat from rising temperatures, Gore challenged delegates packing a meeting hall to forge an agreement with an eye on history.

"Instead of shaking our heads at the difficulty of this path and saying this is impossible, how can we do this, we ought to feel a sense of joy that we have work that is worth doing that is so important to the future of humankind," he said.