Gymnasts will be first into the spotlight with their Olympic trials set for June 19-22 in Philadelphia followed by the track and field trials scheduled from June 27 to July 6 in Eugene, Oregon and the swim trials which will run almost simultaneously from June 29 to July 6 in Omaha.
Johnson and Nastia Liukin, both rated top contenders for the women's all-round title in Beijing, are expected to take their growing rivalry to Philadelphia where the top two finishers will earn automatic selection to the squad. The rest of the six-member team plus three alternates will be selected at a July 20 training camp.
The men's competition is expected to be more wide open with reigning Olympic all-round champion Paul Hamm sidelined with a hand injury.
Despite a broken hand, Hamm still hopes to be fit enough to defend his gold medal in Beijing and has submitted a petition to be included in the US squad.
No American athlete, however, will face greater scrutiny over the next three weeks than Phelps as he bids to set the stage for Olympic history.
The winner of six gold and eight medals at the Athens Summer Games, Phelps has been coy about his programme for Beijing but all will be revealed during the eight-day meet in Omaha, where world records are expected to tumble.
After watching Australian and European swimmers rewrite the record book early in the year, American swimmers will hope to retake the spotlight and hold it through the Beijing Games.
In Eugene, Gay will headline the sprint-dominated US athletics trials but there will be plenty of subplots. Competition will be particularly fierce in the 400 metres, the men's 400 metres hurdles and the men's shot put.
Americans could sweep Beijing medals for those events if the favourites advance through the trials.
World 1,500 and 5,000m champion Bernard Lagat will bid for his first Games in a US vest after twice winning medals for native Kenya.
