Washington (PTI): Accusing India and China of being the greatest contributors to global warming, presumptive Republican Presidential candidate John McCain has said the US will have an obligation to act if the efforts to negotiate an international pact to deal with the problem does not succeed.

McCain made the remarks at a campaign rally in Portland, Oregon in what many analysts have seen as a major departure from the Bush administration's policy on climate change issue.

"We make our own environmental plans and our own resolutions. But working with other nations to arrest climate change can be an even tougher proposition. China, India and other developing economic powers in particular are among the greatest contributors to global warming today - increasing carbon emissions at a furious pace - and they are not receptive to international standards," Mccain said.

"This set of facts and perceived self-interests proved the undoing of the Kyoto Protocols. As president, I will have to deal with the same set of facts. I will not shirk the mantle of leadership that the US bears.. I will not accept the same dead-end of failed diplomacy that claimed Kyoto,"he said.

"If we are going to establish meaningful environmental protocols, then they must include the two nations that have the potential to pollute the air faster, and in greater annual volume, than any nation ever in history," he said in a direct reference to India and China.

"... we will continue in good faith to negotiate with China and other nations to enact the standards and controls that are in the interest of every nation -- whatever their stage of economic development.....and if the efforts to negotiate an international solution that includes China and India does not succeed, we still have an obligation to act," he said.