But he said that a stalling of the U.N. Kyoto protocol, which lays down the rules for cutting emissions of greenhouse gases like carbon dioxide from cars and factories under the Convention, was "a major hurdle to effective global action."

"I call again on those countries that have not yet ratified the protocol to do so, and show that they are truly committed to shouldering their global responsibilities," he said in a statement marking the convention's 10-year anniversary.

Russia has had a casting vote over Kyoto since President Bush pulled out of the protocol in 2001, arguing that it was too costly and wrongly excluded developing nations.

Kyoto will collapse without Russian backing because it must be ratified by countries accounting for 55 percent of carbon dioxide emissions by industrialized countries.

Now backed by states accounting for 44 percent, the protocol needs Russia's 17 percent to reach the goal after the withdrawal of the United States with 36 percent. But President Vladimir Putin has expressed worries Kyoto might limit Russian economic growth.

Bush's father, ex-President George Bush, signed up for the climate change Convention at a 1992 Earth Summit in Rio de Janeiro and told delegates "we must leave this earth in better condition than we found it."

But the World Resources Institute, a Washington-based research group, says global warming is worsening due to increasing use of fossil fuels such as oil to coal.

IRREVERSIBLE DAMAGE?

"We are quickly moving to the point where the damage will be irreversible," said Jonathan Pershing, director of the Institute's Climate, Energy and Pollution program.

Many environmentalists say that global warming is the biggest long-term threat to life on earth. Rising temperatures may drive thousands of species to extinction, trigger more floods or droughts and sink low-lying islands as icecaps melt.

Klaus Toepfer, the head of the U.N. Enviroment Program, urged the United States and opponents of Kyoto in Russia to reconsider their belief that Kyoto is an economic straitjacket.

"The Kyoto protocol is not a recipe for economic disaster," he said. "In the long run, it is likely to generate prosperity and financial savings rather than economic suicide."