Allyson Felix hopes the "breakthrough" 200m run she produced at the US trials will be the springboard for Olympic gold over the distance at the third time of trying.

Felix clocked 21.69sec at the June trials, the sixth-fastest women's 200m ever clocked and the fastest in the world for 14 years, perfect timing for an outing against old rivals at the London Games.

Jamaican Veronica Campbell-Brown won the 2004 and 2008 Olympic 200m titles, but Felix, a four-time world 200m champion, is hoping the tide will change.

"The trials were great for me," she said. "It just encouraged me and hopefully I'll have a great performance here.

Her "breakthrough personal best" in Eugene, Oregon, was "very important for me", she added.

After spending last season running the 200-400m double, Felix will this season focus on the sprint double.

She took her place on the US team's 100m roster in controversial circumstances after tying with Jeneba Tarmoh in the trials, the latter eventually pulling out of a rematch.

But Felix insisted that she had been right not to cede her place to Tarmoh, with whom she remains on good terms and indeed even runs the 4x100m relay.

"This is the Olympics. This is not something that I started last year," she said. "This is not an easy thing. I remember when I first came to (coach) Bobby (Kersee) almost eight years ago.

"I told him that at the Olympics I wanted to run the 100, 200, 4x100 and 4x400m relays.

"At the time he said 'That's a lot but I think we can do it'. And it was right then when we started to train for it.

"There's been heartbreaks, tonnes of ups and downs.

"Everyone sees this one moment (with Tarmoh) and they forget that this is your life plan, this is what you sacrifice enormously for.

"I think a lot of people expected me to give up my spot... but it's not just about me."

Felix lost her world 200m crown to Campbell-Brown in Daegu after her 200-400m double saw her take bronze and silver respectively.

And the 26-year-old admitted that the additional training for the 100m over the 400m had really made a difference.

"Last year I ran the 400m and I didn't have my typical burst of speed," she said. "It was a weird feeling to get to a spot and realise I didn't have that extra gear.

"This year the sprints have helped me stay aggressive."

She added: "I'm really taking each race one at a time.

"Even though I think the 100m helps me a lot for my 200m, I'm still very invested in it and I still think I can do really well. I know the odds are definitely against me.

"I've been working so hard and I think I can still get it done. Once that's done, my attention will turn to the 200m."