Japan, Canada and Australia are undermining talks on a treaty limiting emissions of ``greenhouse gases'' with new demands, environmental activists charged Wednesday.

After the United States disappointed delegations by renouncing the 1997 pact without offering an alternative, efforts to curb emissions that are believed to be heating up the atmosphere are running into further problems.

With the United States standing aside, Japan's role is crucial. The accord can only enter into force if backed by 55 countries, representing 55 percent of the industrialized world's emissions. If Japan pulls out, the second target can't be reached.

Japanese Prime Minister Junichiro Koizumi rattled European leaders last week by suggesting that, after the U.S. pullout, an agreement may not be possible before autumn.

And Japan also joined Canada and Australia in pressing demands that they get more credit for forests that absorb carbon dioxide.

Environmental activists reacted with anger, saying polls show that the public wants the Kyoto pact.

``In essence, they're killing the Kyoto Protocol behind the scenes,'' Jennifer Morgan of the Worldwide Fund for Nature said Wednesday. ``Their negotiators are putting forward hardline, unconstructive positions that move the talks backward.''

European Union countries want stricter limits on counting the beneficial effects of forests and soil than other countries, including the United States.

``Japan in particular is trying to blackmail the European Union,'' said Bill Hare of Greenpeace.

In turn, Japan's environment minister urged the United States to reconsider its position.

``For all countries, participation of the United States is the best scenario,'' Yuriko Kawaguchi said Tuesday as she arrived in Bonn for 180-nation talks on the Kyoto pact, which would cut emissions of gases believed to be heating up the atmosphere.

Kawaguchi insisted Japan does not want to delay the negotiations and would ``do its utmost'' to help bring the treaty into force by next year.

Her German colleague, Juergen Trittin, has said the accord could be salvaged with a compromise to keep Japan on board.

More than 80 countries have signed the Kyoto pact, which requires industrialized countries to cut greenhouse emissions an average 5.2 percent from 1990 by 2012.

President Bush abandoned the pact in March, saying it was flawed and would hurt the U.S. economy. Officials from about 180 nations are meeting in Bonn through next week to try to save it.

The top U.N. official dealing with climate change spoke for many countries Tuesday when he also expressed disappointment at the U.S. stand.

``Everybody wants the United States in,'' Michael Zammit Cutajar said in an interview. ``The U.S. administration still hasn't said what it wants. It has said what it doesn't like.''