By Gene Cherry

(Reuters) - One world record is not enough for Keni Harrison.

Hours after breaking the 28-year-old 100 meters hurdles record on Friday to avenge failing to make the U.S. Olympic team, the young American revealed there is another race she wants to conquer.

"(I want to) try to get another record in the 400 hurdles," Harrison told a conference call from London where she ran a record-breaking 12.20 seconds in the 100 meters hurdles.

She bettered the record of Bulgaria's Yordanka Donkova from 1988 -- four years before Harrison was born -- by one hundredth of a second.

It came in Harrison's first race since finishing sixth in the cut-throat U.S. Olympic trials where only the top three advance to the Games.

"I wanted to come out here with a vengeance to show these girls what I have," said the 23-year-old, who defeated the three women who will represent the United States in Rio.

Harrison was a sure-fired favorite before the American trials to make the U.S. team and win gold at Rio after running the second-fastest 100 meters hurdles ever in May.

"The pressure got to me," she said of the U.S. trials. "I was really heartbroken. I wanted to give up so bad."

But calling it a season was not the answer, she realized.

"I knew this was the only way I was going to make myself feel better, to get back to training and go after that world record," she said.

Harrison said she was nervous before Friday's preliminary race.

"I just tried to push all of the doubt out of my mind... I just told myself you know that you are the best. I just kept saying that over and over again," Harrison said.

A speedy 12.40 seconds in the preliminary restored her confidence. "I'm back," Harrison said to herself.

In the final, "I just told myself, keep going, keep going."

She did, becoming the fastest ever in the event.

Harrison will next make an unexpected trip home to North Carolina and her family of 11 to watch and cheer on her U.S. team mates in Rio before three more races in Europe.

She hopes to wrap up the Diamond League 100 meters hurdles title, ensuring she will have a bye into the 2017 world championships in the event.

"If I do that I have a chance to take a break from the 100 hurdles until world championships and try to get another record in the 400 hurdles," said Harrison.

"My main focus (next year) will be the 400 hurdles until the worlds and I will try to do both."

She ran both events in college but her best of 54.09 seconds in the longer race is more than a second off the world record.

Though heartbroken at missing Rio, the failure has brought a new challenge, she said.

"It is unfortunate I didn't get top three," said Harrison, who is "ok" with the U.S. system.

"But once I try again in a few years, I know getting top three is probably going to be the best feeling in the world, knowing that I conquered so much to get there."

(Editing by Sudipto Ganguly)