The State Duma lower house of parliament 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, widely expected here to be formalities.

Russia held the key to whether the landmark 1997 draft agreement made the jump to becoming a working international treaty and environmental groups hailed Friday's vote.

"We will look back on today as the moment in history when humanity faced up to its responsibility," the Greenpeace environmental group said in a statement.

"We'll toast the Duma with vodka tonight, but on Monday morning we need to roll up our sleeves and get down to the real work," the statement quoted the group's climate policy advisor Steve Sawyer as saying.

Friday's vote resuscitated a pact that until recently was considered all but dead after President George W. Bush announced in 2001 the United States wanted no further part of it.

Approval in the upper house, the Federation Council, and signature by Putin were regarded as virtually assured after the government recommended that Russia approve Kyoto after years of Moscow ambiguity.

In their discussions ahead of the vote, Russian deputies hailed the financial opportunities the pact offered Moscow.

"This protocol gives Russia financial possibilities," said Valery Zubov, a deputy with the main pro-Kremlin United Russia party in the discussion before the vote. "We have a chance to have a cleaner future."

Russia can make a short-term profit by ratifying the protocol since it will be able to sell some of its quotas for "greenhouse" gas emissions to other industrialized signatories.

Point Carbon, a Norway-based consultancy firm, has estimated that Russia could earn 10 billion dollars (eight billion euros) with the treaty's help by

Russian Deputy Prime Minister Zhukov said Russia would likely approach its Kyoto quotas by 2010 if the nation's gross domestic product (GDP) grew by nine nine to 10 percent a year.

But others said Russia had been pressured into ratifying the pact.

"Russia was under unprecedented pressure," said Natalya Narochnitskaya of the nationalist Rodina (Motherland) party. "It's ratification was presented as a stamp of a civilized country" and not based on scientific data.

It is widely believed here that Russia had agreed to ratify Kyoto in return for the European Union -- one of the treaty's major backers -- supporting Moscow's bid to enter the World Trade Organization.

The treaty legally commits industrialised countries to trimming output of six "greenhouse" gases that trap the Sun's heat, gradually warming the Earth's surface and changing its delicately-balanced climate system.

Since it was first drafted in 1997, Kyoto became a tug between the European Union, which strongly supported it, and the United States, which washed its hands of the treaty after Bush assumed office in 2001.

Russia had for years hedged its bets over the pact, but in September the cabinet voted to send it to parliament for approval, drawing a delighted reaction from the EU.

"It's a very happy day for Europe and for me," said Margot Wallstroem, the Swedish EU environment commissioner, after the Russian cabinet vote. "It sends a very forceful signal to the rest of the world."

"It is also very much a victory for the European Union," she said.

Washington has refused to bow to increased pressure to get on board.

"The United States' position on the Kyoto Protocol has not changed," State Department spokesman Richard Boucher said then.

"We thought at this point it wasn't the right thing for the United States, but it's up to other nations to independently evaluate whether ratification is in their national interest."

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