Birchall, who is at Brighton and Hove Albion until the end of the season, has been over a two year deal by the American side, whom he joined after getting out of his contract with Coventry City.
Birchall (7) playing for City Reserves at the start of the season
The Trinidad & Tobago international who joined City from Port Vale will have to end his contract with Brighton to act as cover for David Beckham who is currently with AC Milan.