Palace Malice became the third winner in the three Triple Crown races this year when he saw off Oxbow and Orb to win the Belmont Stakes.

Trained by Todd Pletcher and ridden by Mike Smith, Palace Malice ensured that neither Kentucky Derby-winner Orb nor Preakness champion Oxbow would end the year with two-thirds of US flat racing's coveted treble.

Oxbow, ridden by Gary Stevens and trained by D Wayne Lukas, finished second while Orb, whose late rally under jockey Joel Rosario wasn't enough, was third.

The triumph in the 145th running of the Belmont over a mile and a half (2400m) was Smith's second in the race traditionally dubbed the Test of the Champion. He piloted Drosselmeyer to victory in 2010.

It was especially sweet after the veteran jockey's 2012 season of Triple Crown frustration when he finished second in all three races.

Palace Malice went off at 13-1, but Smith said the longer distance compared to the other Triple Crown events and sweeping turns of the Belmont Park track gave Palace Malice a chance to shine as he failed to do when a tiring 12th in the Kentucky Derby.

The jockey said he was able to get Palace Malice to relax without the blinkers which fired him up in the Derby.

"Today, the whole time he's just enjoying the trip and sucking all the air in," Smith said.

"The whole key was getting him into that rhythm he was in."

Frac Daddy and Freedom Child set the early pace, with Oxbow not far off despite what Stevens called "suicidal fractions".

Stevens took Oxbow to the front down the back but by the time they moved into the final turn Palace Malice was challenging and Orb was beginning a run from far back in the 14-horse field.

Heading into the straight, Palace Malice took the lead from Oxbow and powered to a 3-1/4-length triumph.

"It's huge. It's huge," Pletcher said. "We always felt like he had a big one in him. We were just waiting for it to finally develop."

Stevens was delighted that Oxbow held on for second, calling him "one of the bravest horses I've ever ridden."

Trainer Shug McGauhey said Orb, the 2-1 favourite, just had too much to do at the end.

"He made a good run around the turn, but we had given up so much," he said. "The speed horses held on up front, and we just couldn't catch them."

Eleven horses have completed the Triple Crown sweep of the Kentucky Derby, Preakness Stakes and Belmont Stakes, but the last was Affirmed in 1978.