A joint gathering of major developed and developing nations in Toyako, Japan, on Wednesday agreed that climate change was "one of the great global challenges of our time" and pledged to back a United Nations effort to reach a new climate pact by 2009.

The major economies said they supported long-term and midterm goals for greenhouse-gas reductions, but endorsed no targets.

It came a day after the Group of Eight major industrial democracies set a goal of halving heat-trapping emissions that contribute to global warming by 2050.

The 17-member group that includes developing countries issued its final statement on the sidelines of the G8 summit in northern Japan.

"We support a shared vision for long-term co-operative action, including a long-term global goal for emission reductions, that assures growth, prosperity, and other aspects of sustainable development," the expanded group said.

But the developing nations invited to the gathering were not ready to support the 50 per cent reduction by 2050.

Jim Connaughton, chair of U.S. President George W. Bush's council of environmental quality, said "several" of the emerging economies were willing to support the target, but not enough to allow that language to be put in the declaration. He did not say which nations.

The expanded group included China and India. They were invited to sit at the table with the G8, which comprises Canada, the U.S., Japan, Britain, Germany, France, Italy and Russia.

The statement on Wednesday also pledged to support a UN-led effort to conclude a new global warming pact by the end of next year.

China, India want clear commitments

Environmentalists, however, said the statement was meaningless without targets.

"This whole initiative has been a wild goose chase and hasn't brought anything constructive to the UN talks," said Antonio Hill, of Oxfam International.

Developing nations such as China and India have criticized the G8's position statement for failing to state clearly wealthy nations' commitments.

The G8 statement did not specify a base year for its proposed 50 per cent cut, and the actual emissions reductions and the effect on the environment could vary hugely depending on what year is eventually chosen. Reductions from 2005 levels, for instance, would be far less than from 1990 levels, as in the Kyoto Protocol on global warming.

Still, UN Secretary-General Ban Ki-moon said it was essential to set a long-term goal for global greenhouse emissions by 2050. He said the world cannot afford to wait until 2009, when nations are planning to try to conclude a new global warming treaty to succeed the Kyoto Protocol when its first phase expires in 2012.

The United States has never ratified the Kyoto treaty, with Bush complaining that it puts too much of a burden on the U.S. and other developed countries to reduce emissions while developing giants such as China and India are given a freer rein to pollute as they vigorously compete with America around the world.

Bush will leave office next January, and both major candidates to succeed him have said they are willing to go further in cutting back American emissions.