The European Union, which said last week the global warming issue was an integral part of US-EU relations, expressed concern over the Bush Administration stance. Democrats and environmental groups denounced it.
"The new President came to town saying he would change the tone and change the climate in Washington; I guess we didn't realise it was the real climate he wanted to change," said US House Democratic leader Richard Gephardt of Missouri.
The pact, signed by former President Bill Clinton in 1998 but never introduced in the Senate for ratification, aims to limit industrial-nation emissions of "greenhouse gases" thought to cause global warming.
National Security Council spokesman Sean McCormack said: "We're ready to work with our friends and allies on the issue of global climate change to develop alternative approaches to the Kyoto Protocol."
Asked about last-ditch talks in Bonn in July, he said: "our current plan is to attend the meetings."
Officials later said the US would work with other countries on alternatives to the pact and that it was not considering formally "unsigning" the treaty.
Fleischer said only one of the 55 nations which must ratify the treaty for it to take effect - Romania - had acted, which he said showed other countries agreed with Bush's position.
Among those still to ratify are Japan, the EU, Britain, Russia, China, Norway, Australia and New Zealand.
Bush opposes the pact because it does not also bind developing nations to curb emissions and because he believes the costs outweigh the benefits, Fleischer said.
He said Bush had ordered a cabinet-level review of global warming issues to develop a US response to the issue.
Already this month, the President broke a campaign promise by announcing he would not ask US power plants to cut emissions of carbon dioxide, the gas that a great majority of scientists say is a key factor in the Earth's rising average temperatures.
Bush's carbon dioxide decision followed intense lobbying by coal and oil companies and congressional conservatives who opposed regulation.
Bush today has talks in Washington with German Chancellor Gerhard Schroeder, who asked Bush in a letter last week to abide by the agreement.
The EU has also asked Bush to press ahead with the deal, saying a joint effort to fight global warming was "an integral part of relations" with the EU.
Its Environment Commissioner, Margot Wallstrom, said: "It is very worrying if it is true that the US intends to pull out of the Kyoto Protocol."
An EU spokeswoman said the US had not yet replied to its request for high-level meetings to settle differences over the treaty.
- REUTERS
Herald Online feature: Climate change
Intergovernmental Panel on Climate Change
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Summary: Climate Change 2001
United Nations Environment Program
World Meteorological Organisation
Framework Convention on Climate Change