NAIROBI, Kenya (AP) – Russia formally notified the United Nations on Thursday of its acceptance of the Kyoto Protocol on global warming, starting a three-month countdown for the long-debated 1997 pact on cutting greenhouse gas emissions to come into force.

President Vladimir Putin signed the protocol into law earlier this month, allowing it to take effect in 128 nations that ratified it, said U.N. environmental agency spokesman Eric Falt. The United States has refused to join.

On Thursday, Russia’s permanent representative to the United Nations, Andrei Denisov, turned over the accession documents to U.N. Secretary-General Kofi Annan in Nairobi, where the U.N. Security Council is holding a rare meeting outside its New York headquarters.

“I congratulate President Putin and the Russian Federation for their leadership in making it possible for the protocol to enter into force – as it will, 90 days from tomorrow on Feb. 16, 2005,” Annan said. “This is a historic step forward in the world’s efforts to combat a truly global threat.”

The protocol, ratified by both houses of Russia’s parliament last month, commits 55 industrialized nations to make significant cuts in emissions of gases like carbon dioxide by 2012.

Developing nations like Brazil, China, India and Indonesia also are parties to the protocol but do not have emission-reduction targets.

The United States and Australia rejected the pact, which could not have come into effect without Russia, which accounted for 17 percent of carbon dioxide emission in 1990. The United States accounted for 36 percent of carbon dioxide emissions in 1990.

The Bush administration opposes the protocol because it assigns different levels of carbon dioxide reductions to wealthy and developing countries, a provision it says is unfair.

Industrialized countries will have until 2012 to cut their collective emissions of six key greenhouse gases to 5.2 percent below the 1990 level. Greenhouse gases are believed to trap heat in the atmosphere, warming the Earth.

“A period of uncertainty has closed. Climate change is ready to take its place again at the top of the global agenda,” said Joke Waller-Hunter, head of the Climate Change Secretariat, which services the U.N. Climate Change Convention and its Kyoto Protocol.

Scientists already have detected many early signals of global warming, including the shrinking of mountain glaciers and Arctic and Antarctic sea-ice, reduced ice cover on lakes and rivers, longer summer growing seasons, changes in the arrival and departure dates of migratory birds, as well as the spread of many insects and plants toward the poles.

Africa, which is only responsible for just more than 3 percent of greenhouse gas emissions, is likely to be hit hardest by the impacts of climate change.