The revelation came as Bush said global warming was a "serious long term" problem and the United States was leading research into finding solutions, following a meeting in Washington with British Prime Minister Tony Blair.

Citing documents from the US State Department, the London-based Guardian newspaper said the administration thanked Exxon executives for the company's "active involvement" in helping to shape climate change policy, and also sought its advice on what such policies the company might find acceptable.

This claim was found in briefing papers given before meetings to the US undersecretary of state, Paula Dobriansky, from 2001 and 2004, the daily said.

It also reported that other documents suggested Dobriansky should ask Exxon executives and other anti-Kyoto business groups about potential alternatives to the landmark Kyoto treaty.

"Until now Exxon has publicly maintained that it had no involvement in the US government's rejection of Kyoto," the Guardian said.

"But the documents, obtained by Greenpeace under US freedom of information legislation, suggest this is not the case," it said.

Reflecting a consensus between the company and the US administration on the need for more global warming science and the unacceptable costs of Kyoto, the papers state that Exxon believes that joining the treaty "would be unjustifiably drastic and premature", the Guardian reported.

The papers emerged as Blair wrapped up a lightning US trip in a bid to drum up support for a two-pronged initiative at a Group of Eight (G8) summit in Scotland next month to tackle climate change and poverty in Africa.

The United States has been widely criticised for withdrawing from a commitment to ratify the Kyoto protocol on climate change, which set targets for reducing pollution that causes global warming.

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