Democrat John Kerry (search) calls President Bush's economic policy "an astonishing failure" and promises to protect U.S. jobs in a new television commercial meant to soften criticism of the front-runner's vote for a free-trade pact in states hit hard by job losses.

"We need to be on the side of America's workers," Kerry says in the spot. "George Bush won't do it. I will."

The ad, which will start airing Wednesday in Ohio and upstate New York, was unveiled one day after Kerry said he would not run negative ads if Bush's re-election team promised to do the same.

Kerry and challenger John Edwards (search) are focusing on the economy, trade and jobs in ads and on the campaign trail as they campaign through Ohio, Georgia and New York, three of the 10 states that will hold Democratic nominating contests March 2.

Kerry leads Edwards in delegates needed to secure the nomination and states won in the primary contests.

Kerry aides say he will spend $1.5 million on TV ads in Ohio, Georgia and upstate New York through March 2, but as of Tuesday he had bought less than half of that amount. Edwards on Tuesday was boosting his advertising buys in those states to mostly match Kerry's buys. Both were spending the most in Ohio, buying at least $230,000 worth of ads so far this week.

In recent weeks, Edwards has criticized Kerry for backing the 1993 North American Free Trade Agreement (search) as he campaigns through high job-loss areas. Edwards was not in the Senate at the time but says he would have voted against the pact that he blames for massive job losses.

Kerry's new ad doesn't mention Edwards, but it is designed to blunt the North Carolina senator's trade-focused message in blue-collar areas suffering from the loss of jobs. The ad highlights Kerry's plan to end tax breaks to companies moving jobs oversees and to develop new incentives to keep jobs in America.

Looking toward the general election, Kerry also was using the ad to build his case with voters in Ohio, a critical battleground state, that he should be president.

On Monday, Kerry said that he would run a clean campaign if Bush's campaign promised the same.

"I would certainly agree to run not one negative advertisement if they'd agree to run no negative advertising," Kerry told WNBC-TV in New York in an interview. "But I doubt very much that they'll do that."

Aides say such a request hasn't been made to the Bush-Cheney campaign because Kerry is not yet the nominee. Michael Meehan, a Kerry adviser, said Kerry has set standards in the past, including the tenor of advertising in his 1996 senatorial campaign.

Terry Holt, a Bush-Cheney spokesman, said: "It's a bizarre offer by someone who's yet to run much of a positive campaign."

Holt defended Bush and took a swipe at Kerry, saying "one candidate's economic policies put us on the road to recovery and the other candidate is for higher taxes."

During the Democratic primary season, Kerry has criticized Bush or his policies in at least a dozen TV ads, saying in one that Bush "deserves to be laid off" and talking in others about "Bush's mistakes."

He also has accused Bush of having a "radical agenda" and "working hand-in-hand" with pharmaceutical manufacturers, oil companies and other big businesses. One ad says, "He let corporate lobbyists rewrite our environmental laws, sided with polluters, not taxpayers, and now he's trying to roll back the Clean Air Act."

Bush's re-election campaign hit back two weeks ago on the Internet with a Web video criticizing Kerry. Kerry's campaign responded with its own Web video assailing Bush.