( dpa )- More than 100 pledges from national and city governments, businesses and civil organizations had been collected by the end of a meeting of world environmental ministers and private sector leaders in the US capital.
But the number of commitments made by Thursday fell far short of the 197 made at the first renewable energy conference in Bonn in 2004, and organizers said the door for new pledges would remain open until April 4.
Denmark's Climate and Energy Minister Connie Hedegard told the conference that investors had to be enticed by clear indicators from governments that their money on renewable energy would be well spent.
Denmark was the first country to offer a specific commitment ahead of the Washington Renewable Energy Conference (WIREC), setting a target of at least 30 per cent renewable energy use by 2025.
"You have to create political will," Canada's former prime minister Kim Campbell said of the urgent need to bolster renewable energy use in order to reduce emissions of greenhouse gases blamed for global warming.
Norway laid out its plan to become carbon-neutral by 2050, while Australia set a target of 20 per cent of energy coming from renewable sources by 2020.
A number of smaller island nations threatened by rising sea levels also pledged drastic cuts in their use of fossil fuels. New Zealand said it hoped 90 per cent of its electricity would come from alternative sources by 2025, while Madagascar said it would increase renewable energy use to 75 per cent by the same year.
US officials on Thursday said cultivating renewable energy technology lay at the core of the conference hosts' efforts to cut back on greenhouse-gas emissions, become less dependent on foreign fuel sources, and bolster the sagging US economy.
"Renewable energy is the biggest opportunity for economic growth and wealth creation in our lifetimes," said Thomas Dorr, undersecretary for rural development for the US Department of Agriculture.
Alternative energy has seen a massive uptick in investment over the last few years as scientists have pressed the urgency of tackling climate change and governments - especially in the US and European Union - have become attracted by the prospect of reducing their dependence on oil and gas from foreign countries.
Worldwide, about 71 billion dollars were invested in new renewable capacity in 2007, compared to 40 billion dollars in 2005, according to a report by the Renewable Energy Network for the 21st Century, which was created in 2004 to follow up on the Bonn conference's commitments.
Businesses from around the world offered up their own solutions during a separate private sector meeting and trade show at the Washington conference that lasts until Friday.
US President George W Bush addressed WIREC on Wednesday, offering to help other countries finance clean technology projects and insisting that any plan to reduce greenhouse gas emissions must include commitments from emerging economies.
But environmental group Greenpeace said the US had failed to make any meaningful new commitments to reducing carbon emissions during the conference.
"President Bush has had more than seven years to offer a vision for a renewable energy future for this country and the world but he has squandered that opportunity," Chris Miller, head of climate campaigns for Greenpeace in the US, said in a statement.
WIREC was the third such gathering after similar meetings in 2004 in Bonn and a 2005 follow-up in Beijing. The next meeting has been planned for 2010 in New Delhi.