A £1m prize fund is being offered in an attempt to secure a clash between two unbeaten stars of international flat racing – Frankel and Black Caviar.

Goodwood Racecourse and sponsors Qipco are offering to increase the purse for the Sussex Stakes on 1 August from £300,000 should both horses run.

Frankel, trained in Newmarket by Sir Henry Cecil, has triumphed in his nine starts including last year’s 2,000 Guineas and Sussex Stakes.

Black Caviar has won all 19 races in her native Australia and could run in Europe during the summer.

Sheikh Fahad Al Thani, who helps run Qatar-based investment firm Qipco, said he hoped the financial incentive would help lure the pair to the one-mile Group One race at Goodwood.

“In their respective home countries, Frankel and Black Caviar have ignited levels of public interest matched only by true champions of the past,” he said.

“The sport is blessed to have two such outstanding horses competing at the same time and consequently we felt it would be remiss not to make every effort to try to bring about the race everyone wants to see.

“The Sussex Stakes is arguably the only realistic chance of the two horses meeting, and we are delighted to make the gesture of increasing the prize fund to £1m as an incentive to the connections of both horses to run at Goodwood.”

Frankel has won six races over a mile (eight furlongs), whereas Black Caviar has yet to try the distance and has run mainly over five and six furlongs, with one victory at seven.

Black Caviar, trained by Peter Moody, could run in the six-furlong Golden Jubilee Stakes at Royal Ascot in June and then the July Cup at Newmarket.

“She’d have to come through both those races extremely well to even consider it [Sussex Stakes],” Moody told Sky Sports News.

Frankel is expected to step up in trip from a mile later in the season and Teddy Grimthorpe, racing manager to owner Khalid Abdullah, said the Goodwood prize fund would not affect where the horse ran.

“If we were to stay at a mile then running in the Sussex Stakes is a possibility, but I’m afraid the extra prize money is not going to influence any decisions,” he told the Guardian.