Activists launched what they called the world's biggest campaign to combat global warming on, urging governments to agree a tough UN climate pact at talks in Copenhagen starting in 100 days' time.

Environmental organisations, trade unions, religious groups, scientists, anti-poverty campaigners and others representing tens of millions of people teamed up to put pressure for curbs on greenhouse gas emissions.

"Time is running out," said Kumi Naidoo, chairman of the Global Campaign for Climate Action of the TckTckTck campaign, meant to refer to the sound of a clock ticking as the UN meeting draws closer.

TckTckTck would include actions such as rallies or online advertisements to show, for instance, how people in developing nations are already suffering from global warming and how a shift to green jobs could help recovery from recession.

Last Friday was exactly 100 days from the December 7 start of the two-week meeting in Denmark due to agree a successor to the UN's Kyoto Protocol to rein in changes such as more droughts, floods, rising sea levels, a spread of disease and heatwaves.

"We are deeply anxious that the negotiations are not where they need to be," said Mr Naidoo. TckTckTck calls itself in a statement "the biggest ever climate change campaign".

Mr Naidoo urged a "massive push by ordinary men, women and young people in the remaining 100 days." Two negotiating sessions remain before Copenhagen, in Bangkok and Barcelona.

He said last Friday was the official launch of the campaign, which has already staged some events such as installing a loud ticking noise in a hotel in Bonn where climate negotiators from 180 nations met in June.

Participants include environmental groups Greenpeace and WWF, Christian Aid, Oxfam, the World Conference of Religions for Peace, the Union of Concerned Scientists, an international umbrella group for trade unions, the UN Children's Fund Unicef and a group run by ex-UN Secretary-General Kofi Annan.

"The outlook is looking bleak - but it doesn't have to be," Greenpeace wrote in a report on the state of the UN talks.

It said negotiators were deadlocked over whether developed nations would adopt strong 2020 targets to cut greenhouse gas emissions and whether they would also provide billions of dollars to help developing nations.