RIO DE JANEIRO, Brazil, July 23 - American Sheila Taormina's bid for Olympic glory stalled at the Panamerican Games on Monday with an 11th place finish in the modern pentathlon.

Attempting to become the first woman to compete in three different sports at three different Olympics, Taormina burst into tears at the end of a tough day of competition realising she had let an early chance to secure a spot for Beijing slip away.

Brazil's Yane Marques delighted the home crowd grabbing the gold with Canada's Monica Pinette taking the silver and Mickelle Kelly of the United States bronze.

Along with their medals all three women clinched Olympic berths for their countries.

"It would have been a relief," Taormina told Reuters, her voice faltering. "Being so new to these sports it's really stressful to pick them up in time...

"I was just thinking, please relieve this pressure now. A sport has never made me cry and this one has.

"Maybe what I'm trying to do I question it all the time, maybe it's to much that's why no one has done it."

Taormina claimed a gold medal in swimming at the 1996 Atlanta Olympics and competed in the triathlon at the Sydney and Athens Summer Games. She has spent the last two years trying to establish her credentials in the modern pentathlon, a multi-discipline event that includes, shooting, a 200 metre swim, fencing, show jumping and a 3,000 metre run.

The top ranked American and number three in the world, Taormina had been in position to claim a medal and the coveted spot sitting third going into the fourth event.

The 38-year-old American's medal hopes disappeared in the show jumping, where she scored 100 out a possible 1,200 points when her horse refused to jump.

Taormina will have several other opportunities to qualify for Beijing with next month's world championships in Berlin and the World Cup finals in Beijing in September both offering direct entry to the winner. The remainder of the 36 spots will be filled using the world rankings.

"I've been in this position before with triathlon, but in the moment it's harder to remember those times," said Taormina. "Now I just have to figure out where I need to improve so I can get a spot as well."