BALI, Indonesia — European nations threatened yesterday to boycott American-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, Vice President Gore, a Nobel laureate, said America 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 on Friday, even if it meant putting aside goals for emissions cuts.

“You can do one of two things here,” Mr. 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.”

America, Japan, Russia, and several other governments refused to accept language in a draft document suggesting rich nations consider cutting emissions 25% to 40% 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.

All sides agree it is impossible to deal with climate change unless America 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 America — and, he hopes, by others. The January 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. America 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 European Union warned it would stay away unless Washington drops its opposition to mandatory cuts.

“No result in Bali means no Major Economies Meeting,” the top E.U. environment official, Sigmar Gabriel, said. “This is the clear position of the E.U. 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.

“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 human kind,” he said.

Meanwhile, Mayor Bloomberg, at a U.N. climate conference drawing hundreds of emissions traders, said yesterday the growing carbon cap-and-trade industry is vulnerable to “special interests, corruption, inefficiencies,” and should be replaced by straight carbon taxes.

Speaking of global warming, Mr. Bloomberg said, “Most experts would agree that the way to solve the problem is with a carbon tax.” The Kyoto Protocol, requiring 37 industrial nations to reduce carbon dioxide and other industrial, transportation, and agricultural emissions, has given rise in Europe and elsewhere to carbon cap-and-trade systems, under which businesses that don’t use up quotas of emission allowances sell them to others who need them to overshoot their ceilings.