The treaty, known as the Kyoto Protocol and forged in 1997 in Japan, must be ratified by a majority of industrial nations responsible for global warming in order to take effect.

It aims to cut emissions of greenhouses gases by an average of five percent from 1990 levels by 2012.

"In Marrakesh, the focus will be on completing the translation of the Bonn agreements into legal language," Dutch Environment Minister and outgoing conference chairman Jan Pronk told the opening plenary session.

A last-minute political compromise on the main issues was reached in Bonn three months ago and the Marrakesh session is expected to produce a legally binding document.

"You can put the icing on the Bonn cake," Pronk told delegates, urging them to set aside political differences. "Don't renegotiate a political agreement already reached, just work it out," he said.

U.S. DELEGATION ON SIDELINES

The environmental group Greenpeace sounded a less optimistic note, saying rules already agreed were so weak that they were unlikely to lead to a reduction of greenhouse emissions.

"Even the Protocol's nominal target of a five percent reduction hardly started the process of making the 80 percent reductions needed to prevent dangerous levels of climate change," said Bill Hare, Greenpeace climate policy director.

The Marrakesh conference "must not be muddled with diplomatic doubletalk...the processes that underpin the Protocol must be transparent and open for public participation," he added in a communique.

The United States pulled out of the Kyoto Protocol in March, calling it flawed and harmful to the U.S. economy.

Though represented in Marrakesh, Washington - the world's biggest industrial power and biggest polluter - is not expected to play an active role, delegates said. This made the support of the 15 European Union countries and Russia vital to the success of the meeting.

The treaty will enter into force if ratified by 55 countries responsible for 55 percent of emissions in 1990. Russia produced about 17 percent of those 11 years ago.

So far, 40 nations have ratified the treaty.

Michael Zummit Cutajar, executive secretary of the Climate Change Convention, said there were no obstacles on major issues.

From Russia "what's on the table is larger allowances for the use of sinks," he told a news conference.

"Sinks" is jargon for the forests and farms that absorb carbon from the earth's atmosphere. The deal allows Russia, Japan and Canada to use these widely to reach their goals.

PROGRESS MUST CONTINUE

Moroccan Environment Minister Mohamed El Yazghi, who was elected conference chairman, said last months's suicide attacks on New York and Washington had shocked everyone, but the U.N. climate talks were a clear answer to those who thought they could stop human progress.

"We don't have the right to fail", Yazghi told delegates, urging them to avoid raising new demands.

Acknowledging that world attention might be focused on the U.S.-led strikes on Afghanistan, he said climatic dangers were not the least of the dangers threatening mankind, which must act as one family.

Organisers also stressed the importance of the venue, in Africa and in a Muslim country.

"Widespread poverty, recurrent drought and floods, and dependence on rainfed agriculture, forestry and fisheries make this continent and its people most vulnerable to climate change," said Zummit Cutajar.

Security was tight at the first international conference since the September 11 attacks and all mail addressed to the conference was being checked for anthrax.

Letters laced with the germ warfare agent have turned up in the United States in recent weeks.