American Pharoah will jump from barrier five in the Belmont Stakes in his bid to become the first horse in 33 years to win the US Triple Crown.

A field of eight will run in the Belmont on Saturday (Sunday AEST) with the Kentucky Derby and Preakness winner the 3-5 favourite to emulate Affirmed's 1978 Triple Crown.

Jockey Victor Espinoza is the first jockey to have a third chance at the elusive treble after winning the first two legs on War Emblem in 2002 and California Chrome last year.

"I'm very happy with the draw," Espinoza said.

"Third time's the charm."

Since 1978, 13 horses have won the Kentucky Derby and Preakness Stakes, but failed to capture the Belmont.

Trainer Bob Baffert has a fourth chance at a Triple Crown, having saddled contenders Silver Charm, Real Quiet and War Emblem.

Baffert said American Pharoah was training well but admitted the 1-1/2 miles (2400m) was a query.

"I think we don't know until it happens," he said.

"A mile and a half is a very rare race for most of those three-year-olds and for me.

"So far everything has been right on schedule.

"There haven't been any setbacks so that's the main thing."

American Pharoah won the Kentucky Derby on May 2 by a length over Firing Line and two weeks later crushed the opposition by seven lengths in the Preakness on a sloppy track at Pimlico.

Frosted, a fast-finishing fourth in the Kentucky Derby, was made the 5-1 second choice after drawing barrier six.

Materiality, trained by Todd Pletcher, is at 6-1 after drawing the outside gate.

Pletcher, who has saddled two Belmont Stakes winners, has another runner, Madefromlucky, the winner of the Peter Pan Stakes at Belmont on May 9.

"I envision Materiality being close to the pace and Madefromlucky mid-pack," Pletcher said.

"I like being outside of American Pharoah. We're going to go into the first turn trying to make sure there's an honest pace."