Washington, Nov 3 (IANS): Engaged in an extremely tight White House race three days before polls, President Barack Obama and Republican challenger Mitt Romney are making whirlwind tours of battleground states with a barrage of TV ads.

The last minute push would take Obama Saturday to Iowa, Ohio, Virginia and Wisconsin and on Sunday in a slew of other states. At various stops, he will be joined by former president Bill Clinton and singers Katy Perry, Dave Matthews and John Mellencamp.

On a three-day sprint to Election Day, Romney is swinging through the pivotal states of Ohio, New Hampshire to Iowa to Colorado and, on Sunday, to Pennsylvania.

The Obama and Romney campaigns, along with their respective allied groups, have bought at least $93 million on ads in 11 states for nine days of television time, CNN reported citing a source monitoring ad buys.

Between last Monday and Election Day Tuesday, Mitt Romney and Republican groups supporting him have purchased $63.6 million of television time, including $6.6 million in Pennsylvania, where the president has a four point advantage, while Obama and his allies will spend $30.2 million.

Meanwhile, a CNN/ORC International survey released Friday, shows Obama with a three point 50-47 percent edge in the pivotal state of Ohio, within the survey's sampling error.

The CNN poll is in the range of the three other non-partisan, live operator surveys of Ohio likely voters also conducted entirely after last week's final presidential debate.

The University of Cincinnati's Ohio Poll and an American Research Group survey both indicated Obama with two-point edges and a CBS News/New York Times/Quinnipiac University poll indicated Obama with a five-point advantage. All of those margins were within the sampling errors of those polls.

The gender, generation and income gaps that CNN polls have indicated in other states are readily apparent in Ohio as well, with Obama winning women by 16 points, lower-income voters by 30 points and those under age 50 by 15 points, CNN said.

Romney leads among men by 13 points, and holds the advantage with older voters by 6 points and those making more than $50,000 per year.

Even as the October jobs report showed that the US economy added 171,000 new jobs while the unemployment ticked up to 7.9 percent, voters appear divided about which of the presidential candidates would lead the country toward economic recovery.

According to an ABC News-Washington post tracking poll, 54 percent of likely voters expressed at least some confidence the economy would improve under Romney compared to 47 percent who said the same if Obama wins re-election.

But only 36 percent of likely voters said the president is chiefly responsible for the country's current economic troubles, and many more -- 51 percent -- instead blame former President George W. Bush.