By Gene Cherry

EUGENE, Oregon (Reuters) - Already America's most decorated female sprinter, Allyson Felix launches the most difficult challenge of her career this week.

Despite an ankle sprain that pains her when she runs, the 13-times global champion hopes the July 1-10 U.S. Olympic trials bring her a double ticket to Rio where she hopes to become the third woman to win a 200-400 meters double at the same Olympics.

"It was going to take a whole lot not to get me here," Felix told a news conference on Wednesday.

A freakish weightlifting accident in April produced significant tears in multiple ligaments of her right ankle.

Yet her Rio goal never died, just the means of getting there, with pool workouts and therapy supplanting track sessions for nearly a month.

Now the double gold dream she has nurtured for over a decade will depend on a top-three finish in both the 200 and 400 meters at the trials.

"If I get first, second or third I will be just as happy," said the 30-year-old Californian, who is the Olympic 200m gold medalist and world 400m champion.

Speed has always been a calling card for America's trials, and this year is no exception.

The men's 100 and 200 meters pit world silver medalist Justin Gatlin and former world champion Tyson Gay against IAAF indoor champion Trayvon Bromell and Ameer Webb with world 100m bronze medalist Tori Bowie a double threat in women's sprints.

No event may be more difficult to make, though, than the women's 100m hurdles. The five fastest sprint hurdlers in the world this year, headlined by American record holder Keni Harrison and 2008 Olympic champion Dawn Harper-Nelson, will be vying for three Rio berths.

The men's race will have its intrigue as well with Olympic champion and world record holder Aries Merritt seeking to make the U.S. team 10 months after a kidney transplant.

Four Olympic gold medalists - decathlon world record holder Ashton Eaton, triple jumper Christian Taylor, women's pole vaulter Jenn Suhr and long jumper Brittney Reese - headline the field events.

Meanwhile, Marquise Goodwin will be deciding whether he spends August on the practice field with the National Football League's Buffalo Bills or in Rio.

Prognosticators are forecasting it will be a golden summer for the long-jumping wide receiver.

(Editing by Frank Pingue)