Bali, Indonesia ? European nations threatened Thursday 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 here toward an agreement on launching negotiations to replace the Kyoto Protocol when it expires in 2012.

But the former vice president urged delegations to reach the required unanimous agreement before the conference’s end today, even if it meant putting aside goals for emissions cuts.

“You can do one of two things here,” Gore 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 percent to 40 percent from 1990 levels by 2020, saying specific targets would limit the scope of future talks.

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

In a countermove, the U.S. early today submitted amendments that would introduce the idea of voluntary cutback programs.

Trying to break the deadlock, Indonesian Environment Minister Rachmat Witoelar – the conference president – proposed revised language today dropping 2020 targets for industrialized nations, but reaffirming that emissions should be reduced at least by half by 2050.

Publicly, the Europeans stuck with their position. “We continue to insist on including a reference to indicating an emissions reductions range,” said the European Union environment commissioner, Stavros Dimas, at midday.

But Witoelar’s proposal gave the two sides room to work out a compromise, producing a relatively vague mandate for two years of negotiations.

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 U.S. – and, he hopes, by others. The Jan. 30-31 session in Honolulu is a continuation of September talks at the White House called the Major Economies Meeting on Energy Security and Climate Change.

The U.S. has invited 16 major economies, 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 EU warned it would stay away unless Washington drops its opposition to mandatory cuts.

“No result in Bali means no Major Economies Meeting,” said Sigmar Gabriel, the top EU environment official. “This is the clear position of the EU. I do not know what we should talk about if there is no target.”

The main goal in Bali is to kick-start two years of intense dialogue about how to slow global warming and head off scientific predictions of rising sea levels, worsening floods and droughts, and losing plant and animal species.

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

“I’m very concerned about the pace of things,” he said. “If we don’t get wording on the future, then the whole house of cards falls to pieces.”

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.”