They described the initiative as a complement to the Kyoto Protocol that commits countries to cutting emissions of the greenhouse gases blamed for global warming.
But environmentalists said the new pact lacked firm obligations to cut pollution and that it might undermine the 140-nation Kyoto accord, which went into force on 16 Febuary.
The Asia-Pacific Partnership on Clean Development and Climate, also announced overnight in Washington, aims to create cleaner technologies for energy-hungry economies such as China and India, meeting long-term energy needs while reducing pollution and addressing climate concerns.
"We view this as a complement, not an alternative" to the Kyoto treaty, US Deputy Secretary of State Robert Zoellick said at a joint news conference by the six countries at an annual Asia-Pacific security conference in the Laotian capital Vientiane.
A ministerial meeting to hammer out programmes for the pact will be held in Adelaide, Australia in November.
Temperatures rose about 1
degree in the last century
Emissions of carbon dioxide and five other gases are believed to be behind rising global temperatures that many scientists say are disrupting weather patterns.
Average global temperatures rose about 1 degree in the 20th century, and scientists say that has contributed to the thawing of the permafrost, rising ocean levels and extreme weather.
Kyoto 'a failure'
The United States, which accounts for one-quarter of the world's greenhouse gases, and Australia refused to ratify the Kyoto Protocol, saying it would harm their economies by raising energy prices, and cost five million jobs in US alone.
Their other objection is that pact mandates greenhouse gas emission reductions only among industrial countries and not developing countries like India and China, which is second only to the US in emissions.
"In the end the key to solving these problems is going to
The deal involves developing
be technology ... cleaner technologies, making technologies
more economic," Australian Foreign Minister Alexander
"These things are going to be a lot more effective over time than just political declarations."
Although Downer insisted the new initiative would not undermine the Kyoto Protocol, he made it clear he did not think much of it. Australia's prime minister, John Howard, on Wednesday called the Kyoto pact "a failure" and said "We have to do better."
Global greenhouse gas emissions would have increased 41% from 1990 to 2010 without the Kyoto Protocol, Downer said. With the accord, they are expected to go up by 40% if all countries meet their targets, he claimed.
Downer said a bigger impact on emissions was needed if the efforts were to affect climate change.
"It looks suspiciously as though this will be business as usual for the United States"
Freinds of the Earth
Thursday's joint statement said the countries could collaborate on clean coal, liquefied natural gas, methane, civilian nuclear power, geothermal power, rural energy systems, solar power, wind power and bio-energy.
In the long-term, they could develop hydrogen nanotechnologies, next-generation nuclear fission and fusion energy, it said.
Environmental group Friends of the Earth was skeptical about the pact because it contained no legally binding requirements to cut emissions.
"It looks suspiciously as though this will be business as usual for the United States," said the UK-based group's member, Catherine Pearce.
"A deal on technology, supported by voluntary measures to reduce emissions, will not address climate change," she said.
Zoellick defended the nonbinding clause, saying "one can't just command other parties to do things. You need to try to develop interests and incentives."
Pierre Pettigrew, foreign minister of Kyoto signatory Canada, said the new initiative showed its authors acknowledged the problem. But now they should produce results, he said.
"I still have to wait for the meat. This is an improvement. This is progress. I don't say it in a cynical way. I hope there will be meat," he said.