Stung by criticism of his plan to lease Philadelphia International Airport to private investors, U.S. Rep. Chaka Fattah challenged mayoral rival Tom Knox yesterday to put his money where his mouth was - a $1 million bet on whether Fattah could pull off the deal.

Knox blinked.

The wealthy businessman, who has estimated his net worth at $100 million, turned down the wager but took a shot at Fattah's finances.

"You know, Chaka, I have a million," Knox said.

The exchange took place at the elegant Four Seasons Hotel, at a forum sponsored by the Central Philadelphia Development Corp. The audience of 100 included some of the city's top businesspeople.

Moderator Paul R. Levy, executive director of the Center City District, asked the three candidates participating - Fattah, Knox and Michael Nutter - whether they would continue the city's 10-year tax abatement on new construction.

Fattah, the first to respond, said he would extend the abatement - and as properties returned to the tax rolls, he would devote the money to low-income housing.

Then the congressman threw in a shot at his rivals.

"Neither one of my great friends and competitors here offer any funding plan to deal with the social challenges that the city faces," Fattah said.

Knox was next. He said he supported the 10-year abatement, then added: "I'd like to point out to Chaka that I'm not using, as Dwight Evans said yesterday, 'voodoo economics.' Getting the airport sold is going to be a monumental thing."

Fattah broke into Knox's answer: "Leasing, not selling."

Knox: "Leasing it, selling it, whichever. . . . What I'm criticizing you about is, the fact that we can't."

Fattah: "That we can't do it?

Knox: "No, we can't.

Fattah: "Would you like to bet a million on it? How much would you like to bet?"

Knox: "I'll give you my white paper on it. . . .

Fattah: "Forget the white paper. I want to know whether you want to bet. . . . I guarantee you we can lease the airport."

Levy struggled to restore some civility to the affair. "All right, you're over your 15-second limit," he told Knox. "Mr. Nutter?"

But Nutter stoked the fire. "I'd be willing to give up a minute or two just to get that [resolved]," he said, as the audience laughed.

Knox explained that under federal law, the government has authorized the privatization of only one airport hub, and a leasing agreement for Chicago's Midway Airport is already being drafted.

"I promise you that we're gonna be able to do it," Fattah insisted, referring to a Bush administration proposal to expand the airport privatization program. "I just want to know whether you're gonna put any money on the table. You bet me a million dollars to the Core Philly Endowment Trust Fund."

Knox backed off, with a parting shot: "You know, Chaka, I have a million."

Levy tried again to intervene. "Michael, is it still constructive, or not?"

"I think it's just getting good," Nutter replied, as the audience roared again.

Fattah got in one last taunt at Knox before the forum veered back to the issues: "We'll see what your millions are worth on Election Day."

After the forum ended, Fattah told reporters he was confident that as mayor, he'd be able to strike a leasing deal for the airport within nine or 10 months. He claims it would provide the city with at least $150 million a year for social programs.

Knox said he remained skeptical, but would pass on the wager.

"I don't bet, ever," Knox said. "You're not gonna see me going down to the casinos and putting nickels in the slot machines, whatever. . . . I'm against gambling, I don't like casinos and there's no reason for me to make a bet onstage with somebody who can't afford to pay off." *