The Eagles will play four warm up matches in August including home and away clashes with neighbours Canada and one against Japan in Tokyo.
Several of the Eagles are currently training in Glendale, Colorado with strength & conditioning coach Dave Williams, with the rest of the squad set to join them on July 31.
"The player pool is now reduced to 36 players and the final RWC squad of 30, that will travel to New Zealand, will likely come from this pool," O'Sullivan told the USArugby website.
"Although with three test matches in August there is always the possibility of injuries, which may open up a late call up for some players who could come from inside or outside this pool of 36.
"The three warm-up tests will be very important in terms of making the final selections for the RWC squad and getting players up to match speed before our first pool game on September 11 against Ireland. It is also important we give players an opportunity to stake a claim for RWC spots while at the same time continue to build solid performances over the three weeks in camp," explained the Eagles head coach.
One omission from the squad is San Francisco Golden Gate lock Samu Manoa, who has signed a professional contract with English Premiership Club, Northampton Saints.
"Samu Manoa will not be traveling to RWC," said O'Sullivan.
"Unfortunately, a clause in his contract prevents him from traveling to RWC. While I wish Samu every success as a professional rugby player and respect his decision to take up a contract overseas, it is disappointing we were only made aware of his unavailability for RWC as recently as three weeks ago."
The squad is blostered by several professionals who were unavailable for the Churchill Cup including Leeds Carnegie's Mike MacDonald.
Amongst the forwards, Olympic Club's McClenahan gets an opportunity to impress the selectors. Lock Cameron Dolan, who was part of the successful All Americans that defeated the New Zealand Universities 2-1 this month, joins the experienced pack.
Biarritz wing wing Taku Ngwenya and Saracens full-back Chris Wyles star amongst the backs.
Highlanders wing James Paterson, will be added to the pool if he passes a fitness test on arrival in Colorado at the end of July.
USA Eagles RWC preliminary squad
Forwards: Inaki Basauri (L' Aquila), Chris Biller (San Francisco Golden Gate), Todd Clever (Suntory Sungoliath, Japan), Pat Danahy (Life University), Cameron Dolan (Life University), Eric Fry (Las Vegas Blackjacks), JJ Gagiano (Univ. of Cape Town), Nic Johnson (Unattached), Will Johnson (London Irish), Scott LaValla (Stade Français), Mike MacDonald (Leeds Carnegie), Brian McClenahan (Olympic Club), Mate Moeakiola (Bobigny 93), Shawn Pittman (London Welsh), Hayden Smith (Saracens), Louis Stanfill (Mogliano), Phil Thiel (Life University), John van der Giessen (Utah Warriors)
Backs: Paul Emerick (Life University), Tai Enosa (Belmont Shore), Troy Hall (New York Athletic Club), Colin Hawley (Olympic Club), Nese Malifa (Glendale), Taku Ngwenya (Biarritz), Mike Palefau (Utah Warriors), James Paterson (Highlanders), Mike Petri (New York Athletic Club), Blaine Scully (University of California - Berkeley), Robbie Shaw (Bristol Rugby), Junior Sifa (Nottingham RFC), Andrew Suniula (Chicago Griffins), Roland Suniula (Boston Rugby), Kevin Swiryn (Agen), Zack Test (Unattached), Tim Usasz (Nottingham RFC), Chris Wyles (Saracens)
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