Official release from Portland Timbers
Timbers general manager Gavin Wilkinson made the announcement.
Renken, 18, has been a member of US youth national teams since 2005 and most recently participated in a camp with the US U-23 National Team in Germany last fall. At the club level, he played for the U-19 team of German Bundesliga club TSG 1899 Hoffenheim during the 2010-11 season.
"While only 18, Charles is a talented player who is already accustomed to the professional environment," said Amos Magee, Timbers assistant coach. "We believe he will further flourish with the Timbers."