Declaration Of War (right): Royal Ascot winner likely to run at SandownPICTURE: Mark Cranham (racingpost.com/photos)
Declaration Of War set to join Mars in Eclipse
However, the Aidan O'Brien-trained duo will not be joined by Camelot, last season's Guineas and Derby champion.
Coral introduced Declaration Of War into their Eclipse betting as 7-2 second favourite on learning of the news, with Al Kazeem heading the market at 13-8.
O'Brien said on Wednesday: "There is a strong possibility that Declaration Of War will run in the Eclipse. A final decision will be made early in the morning. We plan to run Mars in the race.
"Camelot will not be running. We're giving him a break."
In recent days O'Brien has discussed retirement as an option for Camelot, who has lost his last two races to Al Kazeem and struggled to recapture the form of his three-year-old season.
Declaration Of War is a best-priced 4-1 for the Coral-Eclipse, while Mars, an unlucky sixth in the Derby at Epsom, is no bigger than 5-1.