"I believe you can say that we took a step forward," Japanese Prime Minister Shinzo Abe told a news conference after a summit meeting with US President George W. Bush at Camp David.

"We will continue to work closely together on this issue."

In a joint statement issued after the meeting, the two leaders agreed that dealing with climate change and energy security requires sustained global action.

"We remain committed to the ultimate objective of stabilizing greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous ... interference with the climate system," the statement said.

"We will further explore the steps forward to this objective," it added, saying these would include cooperation on clean energy technology and energy efficiency, including alternative and renewable fuels such as nuclear energy.

"We are working to ensure that the energy on which our economies depend remains reliable, affordable and secure."

But the statement was short on concrete steps and no mention was made of any US participation in any post-Kyoto framework.

Abe said in a television interview on Monday that he hoped to find ways for the United States, the world's largest emitter of greenhouse gases, to cooperate in future pacts.

Japan and the United States this week signed an agreement on nuclear energy cooperation, which the two leaders welcomed.

Under the agreement, the two countries will work together on developing advanced technology which will recycle nuclear fuel into a form difficult to use in weapons.

The two sides will also eventually try to set up an international framework under which countries without means to reprocess their spent nuclear fuel could outsource the task to those with the advanced technology.