The Sounders on Friday acquired the rights to striker Kenny Cooper and allocation money from FC Dallas for midfielder Adam Moffat.
The move comes after Seattle this week added goalkeeper Stefan Frei and center back Chad Marshall, while parting ways with goalkeeper Michael Gspurning, defender Marc Burch, and midfielders Mauro Rosales and Steve Zakuani.
Cooper, whose option was declined by Dallas, still needs to agree to terms with Seattle. After notching 18 goals in 2012 with the New York Red Bulls, the 29-year-old returned to the Dallas club he played for from 2006 to 2009 but only scored six times in 31 appearances.
"Kenny is a proven goalscorer who is extremely active in the box," Sounders coach Sigi Schmid said in a news release. "At 6'3, he is a big forward who creates matchup problems for opposing defenders."
Moffat spent just three months with Seattle, playing in six regular season matches and three playoff games following a September trade from the Houston Dynamo. The 27-year-old started the 2011 and 2012 MLS Cups for Houston.