The European Union executive has welcomed the Russian parliament's ratification of the Kyoto Protocol on global climate change - and has called on the United States to follow suit.
However, Washington poured cold water on the EU demands, saying the United States remained opposed to the climate change treaty and had no plans to sign it.
EU environment chief Margot Wallstroem stressed Europe's leading role in backing Kyoto, while outgoing European Commission chief Romano Prodi said the news was good for generations to come.
"No news could be more welcome in my last few days in Brussels," said Prodi, who is due to leave office next week at the end of his five-year term. "We are happy that the Russian Duma has decided to ratify.
"We hope that the United States will now re-consider its position," he added.
The comments came after the Russian Duma approved the pact by a vote of 334 to 73, with two abstentions, paving the way for endorsement by the upper chamber and signature by President Vladimir Putin.
But Washington's refusal to back it has raised the biggest question mark over the 1997 Kyoto pact. US President George W. Bush ditched the agreement shortly after coming to office in 2001.
Wallstroem, who noted that Europe had "led the way" in facing up to the challenge of climate change, said it was unclear whether next month's US presidential election will change anything soon.
"I am not sure what a victory for (US Democratic challenger John) Kerry to climate change policy would mean," she told reporters.
But she agreed that Moscow's move boosts the pressure on Washington. "I think it creates more of a pressure ... you cannot ignore the more than 126 (nations) that have ratified" Kyoto, she said.
That pressure had no noticeable effect on the United States, with deputy State Department spokesman Adam Ereli saying "we have no intention of signing or ratifying (Kyoto). We have not changed our views."
Those views - that Kyoto would be too much of a burden for US industry or US consumers, who produce 25 percent of the world's carbon dioxide emissions and are the biggest consumer of fossil fuels - have made Washington the target of international condemnation.
Since Bush abandoned the protocol, Russian support has been essential for Kyoto to take effect as an internationally binding treaty.
The EU environment commissioner underlined that Kyoto's entry into force will accelerate the emerging global market in greenhouse gas emissions, of which Russia could be a key beneficiary.
Russia's greenhouse gas emissions are currently some 30 percent below 1990 levels. Kyoto requires that Russia not exceed the 1990 levels during 2008-2012, she noted.
"This means that, once international emissions trading starts, Russia will have a significant surplus of emission quotas that it can sell to other countries that have ratified the protocol," Wallstroem said.
Prodi underlined that the Russian ratification was only a "first step."
"It needs to be followed by others. We must not let up on this issue but keep pushing it with all our force," he said.
"We are seeing an example of serious commitment that we share. I hope that example will be followed by those who have not yet signed the Kyoto Protocol, starting with the United States."
For Wallstroem, Moscow's move caps her five years in charge of the EU environment brief, which she will trade in for a new job as communications chief in a new commission scheduled to take office on November 1.
"We are now happy to have Russia on board and we can now put words into deeds," she said, calling for champagne glasses at a hastily arranged Brussels press conference.