Earth Hour's CEO and co-founder Andy Ridley speaks at a press conference in Singapore on February 27, 2013. A campaign by global environmental movement Earth Hour to get promises of action from individuals and organisations has spread to at least 50 countries, its chief executive said Wednesday.

A campaign by global environmental movement Earth Hour to get promises of action from individuals and organisations has spread to at least 50 countries, its chief executive said Wednesday.

Andy Ridley said the "I Will If You Will" campaign, launched in 2012 in 13 countries, is expected to expand its geographic reach almost fourfold this year, strengthening the group's impact beyond an annual lights-out event.

"Last year we rolled out 'I Will If You Will' to 13 countries and territories so it's basically a to see if it would work," Ridley told journalists in Singapore.

"It worked. So this year, instead of 13, it will be at least 50, we already have at least 50 countries confirmed."

Last year the campaign spurred a 120,000-strong petition in Russia that galvanised parliament to pass a law protecting the seas from .

Former Botswana president Festus Mogae also pledged to plant one million indigenous trees in four years.

The countries involved last year included Singapore, Sweden, Hong Kong and the United States. This year's participating countries include Australia, Britain and , with celebrities expected to make pledges.

Singapore-based Earth Hour's headline campaign is an annual lights-out activity to underscore . It was observed in 7,000 cities and towns in 152 countries and territories last year, the group said.

This year's Earth Hour is scheduled for March 23 at 8:30 pm in participating locations.

Ridley, speaking at the global of Earth Hour 2013, said the Asia-Pacific region gives the movement its strongest support.

"Asia-Pacific, as a region, is by far the strongest, and is probably the second," he said.

"Many campaigns are based out of Europe and based out of the US, Earth Hour is not and maybe that's a really good strength for us."