China, India and other developing nations must join industrialized countries in reducing greenhouse gas emissions if the world is to avert a global warming disaster, former British Prime Minister Tony Blair said at a climate change conference Saturday.

An agreement to succeed the Kyoto global warming pact that expires at the end of 2012 will have to find a way to include developing nations, while allowing them to grow their economies, Blair told the meeting of 20 nations.

“The dilemma is this: how to cut a deal that has both the developed and developing in it, recognizing that the obligations on the one can’t be the same as the obligations of the other,” Blair said at the opening session of the conference outside Tokyo.

He noted China and India are on the verge of a transition from rural to industrialized economies _ setting the stage for a huge rise in emissions. China now generates a large share of the world’s greenhouse gases, with some experts saying it has already overtaken the U.S. as the world’s No. 1 emitter.

Carbon dioxide and other pollutants are blamed for the rise in global temperatures.

Developing countries say rich countries have the primary responsibility for reducing emissions, while poorer nations need to grow their economies. The United States and other wealthy countries are eager to include growing economies such as China and India on the next global warming pact.

Blair said it would be unfair to deny developing nations the chance to expand. He said the United States, Japan and Europe _ where per capita emissions are far higher _ should bear the largest burden.

But all nations should share in the solution, he said.

Blair was addressing the conference in his role as a consultant to The Climate Group, a nonprofit organization funded by corporations and governments from around the world. His aim is to rally support for a global pact to cut greenhouse gas emissions by 50 percent by 2050.

A U.N. conference in Bali in December struck a deal to conclude an anti-global warming pact by 2009, to take effect in 2013, but nations did not agree on a 2050 emissions target.