Japanese government officials said today they were preparing to ratify the Kyoto agreement on global warming even without US participation.
Tokyo, which has yet to officially endorse the pact, has been in a quandary after the US backed out of the protocol in March.
Europe has been pressuring Tokyo to proceed with the pact without the US, but Japan - the host of the Kyoto convention in 1997 - has been stalling, saying it wanted to try bringing Washington back on board.
"The United States's return to the protocol isn't a prerequisite for Japan's ratification," an Environment Ministry official said. "It would be best to have the United States but there are other methods," he said.
Last month, 180 countries reached an agreement in Bonn that should allow the pact to come into force, but delegates failed to agree on details of the implementation, leaving the specifics to be drawn up in October at the next round in Morocco.
The pact must be ratified by 55 countries, or by countries accounting for 55 per cent of 1990 greenhouse gas emissions. Participation by Japan, the world's second-largest economy, is therefore crucial in the absence of the United States.
The United States produces 36.1 per cent of the developed world's emissions of man-made carbon dioxide; the EU accounts for 24.2 per cent. Japan is responsible for 8.5 per cent.
Under the deal, industrialised nations agreed to cut carbon dioxide emissions by an average 5.2 per cent from 1990 levels by 2012.