US presidential candidates John McCain and Barack Obama are making their final push for the White House across an electoral map markedly different from four years ago.

It proves Obama's success at putting new states into contention and limiting McCain's options in the final hours, the New York Times reported yesterday.

Obama was using the last days of the contest to make incursions into Republican territory, campaigning Saturday in three states --Colorado, Missouri and Nevada -- that Republican President George W. Bush won with relative ease in 2004.

In what seemed as much a symbolic tweak as a real challenge, Obama bought advertising time in Arizona, McCain's home state.

Meanwhile, McCain started Saturday in Virginia, a once-solidly Republican state that Democrats now feel is within their grasp.

But he then turned his attention to two states that voted for Democratic in 2004 -- Pennsylvania and New Hampshire -- reflecting what his aides said was polling in both states that suggested the race was tightening.

Still, his decision to spend some of his time in the final hours on Democratic turf signaled that McCain had concluded that his chances of winning with the same lineup of states that put Bush into the White House was diminishing.

McCain's hopes appear to rest in large part on his ability to pick up electoral votes from states that Senator John Kerry won for the Democrats four years ago.

The campaign's final days brought a reminder of how Obama's financial might had allowed him to redraw the political map.

Yesterday, Obama will visit Florida, North Carolina and Virginia, which went Republican four years ago.

His campaign manager, David Plouffe, said the campaign was confident of holding onto New Hampshire and Pennsylvania.

McCain and his advisers said they saw evidence they were gaining on Obama as McCain hammered away at his message that Obama would raise taxes.

But the bulk of his last-minute campaign spending and appearances by McCain were in places like Florida, North Carolina and Virginia.

"If the race were closer, the states McCain should be going to would be blue states," said Matthew Dowd, chief strategist to Bush in 2004.

"He's campaigning as if he knows he's significantly behind," he added.