Triple Crown winner American Pharoah has had an easy gallop at Monmouth Park, his final work-out before the $1.75 million Haskell Invitational.

The overwhelming 1-5 favourite for the race on Sunday (Monday AEST) was on the track shortly after 7:30am on Saturday.

He slowly jogged from the barn area to the finish line, giving fans who lined the rail a good look at the first Triple Crown winner in 37 years.

He then turned toward the inside fence for a one-mile (1600m) gallop under clear skies and a cooling breeze rippling off the nearby ocean.

Bob Baffert's assistant trainer Jimmy Barnes said everything was going to plan.

"The track was good, the weather was good," Barnes said.

"He looked awesome out on the track. We couldn't be happier."

The Haskell will be American Pharoah's first start since he swept the Kentucky Derby, the Preakness and the Belmont Stakes. A record crowd that could reach 60,000 is anticipated.

There's been only one minor glitch since American Pharoah arrived in New Jersey.

He reared slightly on Friday when he came through the tunnel to the saddling area, part of the dress rehearsal for race day.

One of his handlers slipped and fell but neither the stablehand nor the horse suffered any injury.

Barnes blamed the minor incident on American Pharoah's sensitive hearing. He runs with cotton stuffed in both ears to deaden distracting sounds.

"Somebody was running in flip flops and it echoed in the tunnel," Barnes said. "He's sharp right now, and he just took off."