Bernie Ecclestone's financial demands are being blamed for putting the future of the United States GP at risk.
Ecclestone and Indianapolis Motor Speedway chief Tony George twice met during the recent event to discuss a new contract to continue the race at the legendary venue.
The original deal that brought the grand prix back to America in 2000 expired in 2006, when a one-year extension was signed.
With that contract now up, IMS CEO George wants a long-term deal, with a deadline looming of July 12 by which time all parties have to agree.
Veteran racer Al Unser Snr, one of only three men to have won the Indy 500 four times, believes Formula One has a future at the track.
But the two-time CART Champion fears money is an issue, saying: "Basically, that's what it comes down to.
"The purses asked for are pretty high, so how do you find sponsors to capture that kind of money?
"It is the reason why Formula One moved from Long Beach, Watkins Glen and Detroit, among others. They all talked about the money. They couldn't afford it.
"Other than that, I feel the US loves it. I don't think in any way they feel it is bad racing. It's good racing.
"But if the organisers can't afford it then it makes it difficult to host."
The 68-year-old is a Formula One fan, and is hoping America has not seen the last of the sport for some time to come.
"I think it has a future at Indy," assessed Unser Snr.
"It draws a good crowd, so I hope it stays. The racing fraternity should enjoy all types of racing, whether it is F1, drag, stock cars or IndyCars.
"I hope it comes back to the US and stays. I would like to see it grow, I really would."
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