U.S. President Barack Obama said on Thursday the United States would lead by example in combating climate change so that developing nations such as India and China would follow suit.

Speaking at the G20 meeting of major economies, he used his presidential debut on the world stage to contrast his policies with those of former President George W. Bush, who had twinned U.S. action to curb climate greenhouse gases with pressure on emerging economic powerhouses.

China and India ... justifiably chafe at the idea that they should somehow sacrifice their development for our efforts to control climate change, Obama told a news conference at the conclusion of the London summit.

He told reporters he had pledged U.S. climate leadership in a meeting with Indian Prime Minister Manmohan Singh.

We talked about ... how important it is for the United States to lead by example to reducing our carbon footprint so that we can help to forge agreements with countries like China and India.

Obama said that developing countries such as China, the world's top carbon emitter, must also act on the climate, but used a light touch which may bode well for U.N. talks meant to forge a new climate treaty in Copenhagen in December.

If China and India with their populations had the same energy usage as the average American then we would all have melted by now, he said.

Developing countries say that the developed world has earned its wealth from more than two centuries of industrialization, spewing carbon dioxide into the atmosphere in the process from burning fossil fuels like coal and oil.

They say the North must act first and help pay the bill for carbon cuts in the South.

The main outcome of the G20 summit was a $1 trillion pledge to rescue the global economy. Leaders also re-affirmed a previous commitment to sign a U.N. climate deal this year, and accelerate the transition to a greener economy.

George W. Bush Barack obama Climate change Climate