"This means that the EU will complete the ratification (of the Kyoto treaty) by June 1," said European Commission spokeswoman for environmental affairs Pia Ahrenkilde-Hansen after EU environment ministers agreed to ratify the pact.

The legal move, which means EU member states may face court action if they fail to reach their emissions targets, confirmed the bloc's chosen position as defender of the global warming treaty, said EU Environment Commissioner Margot Wallstrom.

"It allows us to maintain our credibility and strengthen our leadership role on climate change," Wallstrom told a news conference after the meeting.

The 1997 United Nations treaty commits the EU to reduce its emissions of "greenhouse gases" by eight percent of 1990 levels during the five-year period 2008-2012.

The main gas concerned is carbon dioxide (CO2), emitted when fossil fuels are burned. The gases trap heat in the earth's atmosphere and many scientists believe concentrations are getting so high they will cause disastrous climatic changes.

But U.S. President George W. Bush pulled out of the pact last year saying it would hurt the U.S. economy and last month produced policies to encourage industries to trim emissions.

LACK OF TARGETS

The plan lacked the absolute targets and mandatory aspect of Kyoto, prompting criticism from many governments.

Since the U.S. pullout, the EU has led a diplomatic offensive to ensure countries such as Russia, Japan and Canada stick with Kyoto, and said it would ratify before a global summit on sustainable development to be held in Johannesburg in August and September.

Kyoto cannot come into force until it is ratified by at least 55 countries representing 55 percent of developed countries' carbon dioxide emissions.

As the United States produces one third of those emissions, almost all other developed countries must ratify Kyoto if it is to come into legal force. The EU produces 24.3 percent.

At U.N. climate talks in Marrakesh, Morocco, in November, Russia, Japan and Canada said they would ratify but have yet to do so. The EU will urge them to do so before Johannesburg, Wallstrom said.

The environmental group Greenpeace said the EU's formal decision to ratify should cause Washington to ditch its strategy which, the group claimed, was a gift to the oil industry.

"After President Bush slammed the door on the Kyoto Protocol in March 2001, and the very bad joke of the Bush-Exxon climate plan last month, it is now time for the USA to come back to the Kyoto Protocol," Greenpeace's Michel Raquet said.