King Charles III's horse Desert Hero has been ruled out of the Sydney autumn carnival, but trainer William Haggas has confirmed stablemate Dubai Honour is locked in for an Australian return.

Haggas said it was only in the past 24 hours that it had been decided Desert Hero, who had been among the leading fancies for the Sydney Cup (3200m), wouldn't be making the trip, however, he remained open to travelling the horse in the spring with the Melbourne Cup an option.

"We decided definitely this morning that His Majesty's horse will not be coming to Sydney in the autumn," Haggas told RadioTAB Australia on Thursday.

"We may well come down at the backend of the year in your (Australian spring), but I just felt he needed a bit more time and they (his owners) concurred."

Haggas will have at least two horses in carnival contention with Dubai Honour on target for a defence of his Ranvet and Queen Elizabeth Stakes titles, while Post Impressionist is on a Sydney Cup path.

Dubai Honour has had his program geared around Sydney's autumn features since his successful raid last year and Haggas hopes it's not the last time the horse makes the journey.

"His whole (European) summer was based around getting him in top shape to come to you in February, March," Haggas said.

"He will be the same horse he was, I hope.

"I'd like him to come back for two years. If all goes well this year and he runs competitively, then basically it will be all the same again."

Haggas is yet to shore up a program for the Lloyd Williams-owned Post Impressionist but says the Sydney Cup is the main goal with the NE Manion Cup a possible lead-up.

"He doesn't mind the cut in the ground, and he doesn't mind quick ground either," Haggas said of the stayer, who has firmed from $15 into $11 for the Sydney Cup.

"He's a pretty durable horse, a very sound horse and he should be competitive."

Haggas could have two Queen Elizabeth Stakes runners with the trainer warming to middle-distance horse Mujtaba joining his Sydney squad.

He also confirmed Tom Marquand would again make the trip to Sydney to partner his team, with the star jockey to open his account at the first Group 1 meeting of the autumn on March 2.