Philadelphia announced Thursday it will introduce its newest player at a press conference at PPL Park on Friday at noon (ET), and the Washington Post, Fox Sports and CSNPhilly.com have all reported the 22-year-old has agreed to terms with the Union.
Adu who debuted in MLS as a 14-year-old in 2004, would be reunited with former coach Peter Nowak, who coached D.C. United from 2004-06. Adu played for United from 2004-06, then joined Real Salt Lake in 2007. He signed with Benfica later that year, and spent time on loan with four different club teams.
In 87 appearances for United, Adu scored 11 goals. He was a two-time all-star.
Chivas USA had the top place in MLS's allocation order, but passed on Adu and the Union claimed him in the second spot. Adu struggled after he left MLS, but revived his career after former U.S. boss Bob Bradley called him into the team for the recent CONCACAF Gold Cup.
He was also named to the roster for new coach Jurgen Klinsmann's first match, a friendly with Mexico on Wednesday, but did not make the gameday roster.