COPENHAGEN? (UPDATE) A planetary chain of protests headed by a mass rally in Copenhagen on Saturday cranked up the heat on problem-plagued talks to build a pact to roll back climate change.

The centre of the Danish capital was in virtual lockdown, with thousands of police deployed or on standby ahead of a six-kilometer (four-mile) march that would take green and anti-capitalist demonstrators to the UN conference venue.

"All week we have heard a string of excuses from northern countries to make adequate reparations for the ecological crisis that they have caused," said activist Lidy Nacpil of the Philippines, from a group called the Jubilee South Coalition.

"We are taking to the streets to demand that the ecological debt is repaid to the people of the South."

Within the Bella Center congress hall, Nobel prizewinner Archbishop Desmond Tutu was to lead children in creating "a sea of candles" representing a call from generations imperilled by climate change.

From Australia to the Arctic Circle, protestors readied banners and chants, urging the 12-day marathon to meet the threat posed by Man's meddling with the climate system.

Scientists say rising concentrations of greenhouse gases ? mainly the invisible byproduct of burning oil, gas and coal ? are trapping solar heat, warming Earth's surface and disrupting weather patterns.

If these emissions fail to peak less than a decade from now, the world is doomed to more vicious droughts, flood, rising seas and storms, spelling hunger, homelessness and disease for millions, the experts say.

In Australia, organizers said around 50,000 people had taken to the streets nationwide, wearing sky-blue shoelaces in a call for a strong and binding agreement in Copenhagen.

In Hong Kong men, women and children marched, some dressed as pandas, while others held life rings bearing the slogan "Climate Change Kills. Act Now. Save Lives."

Indonesians rallied in front of the US embassy in Jakarta calling for help for developing nations in reducing greenhouse gases.

A crowd chanted "US is the biggest emitter" and unfurled banners that read "US is the carbon mafia leader" and "Be a part of a legally binding agreement".

If all goes well, the 194-nation conference under the UN's Framework Convention on Climate Change (UNFCCC) will wrap up on Friday with a historic deal sealed by more than 110 heads of state and government.

It would commit major economies to actions that would curb their carbon emissions and set up a financial machine to generate hundreds of billions in dollars for poor countries most exposed to the ravages of climate change.

But since the start of the talks on Monday, progress has been negligible and the mood soured by finger-pointing.

A draft blueprint, presented on Friday, ran into problems almost immediately among the three main groups of players -- developing countries, emerging giant economies and the United States.

Poorer countries lashed it for failing to spell out commitments on finance while the United States complained it failed to bind China and other high-population, fast-growing economies to tough pledges on emissions.

Conference chair Connie Hedegaard scheduled an informal meeting with environment ministers on Saturday in the first of what is likely to be a grueling effort to break the deadlock.

Formal talks begin early next week, culminating in the summit next Friday.

Those rostered to attend include US President Barack Obama, Russian President Dmitry Medvedev, Premier Wen Jiabao of China, Indian Prime Minister Manmohan Singh, Brazil's President Luiz Inacio Lula da Silva, Prime Minister Yukio Hatoyama of Japan and the heads of the European Union (EU).