"We will have 122 countries involved this weekend," said Ian Kiernan, the chairman of the campaign, who estimated that more than 600 grassroots groups reaching 35 million members would be cleaning up from China to Canada.

"It's another form of protest," he told Reuters, saying the presence of volunteers sweeping up schools in Togo or fishing trash out of the Mediterranean was a way of putting pressure on governments and industry to safeguard the environment.

Some of the trash, like metal and paper, gets recycled in the campaign, run in partnership with the UN Environment Programme (UNEP).

"Clean Up the World mobilises people around a powerful idea -- taking the challenge of environment and sustainable development to our front doors, our back yards and everywhere else around the world," said Achim Steiner, head of UNEP.

Among the schemes, children, divers and other volunteers will clean up Rio de Janeiro's Copacabana Beach, the campaign said in a statement. And activists from 14 countries around the Mediterranean plan to clean up the sea.

YANGTZE, NILE

In China's Shaoxing province, volunteers aim to pick up trash around the Yangtze river delta. In Egypt, groups will work to clean up the Nile.

Kiernan, a yachtsman, began with a clean-up of Sydney harbour in 1989 after being shocked by trash in the oceans. He said Sydney was now "sparkling clean" but that worldwide "marine debris is a huge problem and getting worse."

He accused some cruise companies of dumping waste at sea.

"They're making money out of the beauty of the world's oceans and messing them up. We want to get people involved to say: 'That is no longer acceptable behaviour'," he said.

He also said that pollution and global warming, widely blamed on human burning of fossil fuels, were part of a what he called a global environmental crisis.

"The actions of humanity are the cause," he said. "We are the only potential solution apart from extinction."