Senator Obama's plan calls for an expanded use of ''clean coal'', solar energy, windpower, the development of new biofuels, cuts in consumption and the creation of five million new jobs in the ''green energy'' sector.

But Senator McCain argued the ambitious blueprint would fail without an immediate expansion in offshore oil and gas prospecting and a new generation of nuclear power plants. ''Anybody who says that we can achieve energy independence without using and increasing these existing energy resources either doesn't have the experience to understand the challenge we face or isn't giving the American people some straight talk,'' he said in Pennsylvania.

Senator McCain's campaign denied the senator had taken ''big oil'' donations, and accused Senator Obama of trawling for contributions himself from oil industry employees.

Senator McCain's spokesman, Tucker Bounds, said, ''Barack Obama's latest negative attack ad shows his celebrity is matched only by his hypocrisy.''

Republicans also pounced on Senator Obama's call yesterday on the US Government to sell 70 million barrels of oil from the US Strategic Petroleum Reserve in a bid to lower prices, pointing out that he had opposed such a plan a month ago.

Senator Obama's foes also accused him of backtracking for political gain on the question of expanding offshore drilling, which he opposes but now says he would accept if it would ease political deadlock over sweeping energy reforms.

Republicans also mocked Senator Obama by delivering tyre gauges to reporters, highlighting the Democrat's comment that drivers could save gas by properly inflating tyres, which Senator McCain claims is proof the Obama energy plan is shallow. The Obama campaign noted, however, that federal energy and auto racing authorities told drivers to keep tyres inflated to improve mileage.

Senator Obama's assault on Senator McCain coincided with a Rasmussen daily tracking poll showing the two rivals locked in a tie at 44 per cent each ahead of the general election on November 4.

When undecided voters who were ''leaning'' to one candidate or the other were included, Senator McCain led by 47 to 46 per cent, the first time he had posted an advantage since Senator Obama secured the Democratic nomination in June.

The latest Gallup daily tracking poll on Monday had Senator Obama up by three points, 46 to 43, after his lead dipped to just one point late last week. After he returned from a triumphant tour of Europe a little more than a week ago, Senator Obama had led the Gallup poll by nine points.

There was encouraging data for Senator Obama, however, in another survey, which showed him leading Senator McCain by 10 points, 47 per cent to 37, among low-wage white workers. AFP