By Jack Stubbs

RIO DE JANEIRO (Reuters) - When American Will Claye took to the track in the men's triple jump final on Tuesday, he had more than just a medal in his sights; he was also keeping a close eye on his bag.

"I had my eye on that backpack," he said. "Win, lose or draw this was something I felt like I had to do today."

After claiming his second Olympic silver medal in four years with a jump measuring 17.76 meters and watching his American team mate Christian Taylor take the gold, Claye produced a diamond ring and leapt into the stands.

Draped in an American flag, he dropped to one knee in front of long-term girlfriend Queen Harrison and asked her to marry him. She said yes.

"When I woke up I was like, today is going to be the best day of my life," he told reporters. "I'm going to go out there and do what I have to do on the track and I'm going to make her my fiance after that."

Claye is not the first Olympian to ring the wedding bells in Rio and crowds at events including equestrian, diving and women's rugby have all been witness to public marriage proposals at the Games.

The 25-year-old said his proposal to sprinter and hurdler Harrison, his girlfriend of five years, had been a secret with only two of his new fiancé's closest friends in on the plan.

"She just burst into tears... she didn't have any clue," he said, describing Harrison's reaction.

"I was just worried about what I had to do on the track... I was hoping nobody would propose to her first."

Taylor said he had no idea of his rival's intentions beyond the competition when he jumped 17.86 meters on his first attempt to clinch his second consecutive Olympic gold.

"I don't know if I'd be able to do that," he said. "I'm proud that he made the most of this moment."

A competitor at the 2008 Olympics in Beijing, the 27-year-old Harrison had also hoped to run in Rio and would have been on the track in the women's 100 meter hurdles at the same time as Claye's jump event had she qualified.

"I feel like it trumped the hurt she had from not making the team," Claye said of his proposal.

"She was supposed to be here competing too, her event was going on at the same time, I know how much that hurt."

(Editing by Clare Fallon)