Lowry announced Monday on Instagram that his surgically-repaired thumb has not recovered enough to participate in USA Basketball's camp.
"I was hoping [to] be cleared and ready for the tournament but I was not cleared for full basketball activities," Lowry wrote. "I was hoping to be available in time to help my country in their quest for gold this upcoming tournament.
"I love playing for USAB but I have to sit this one out and support the team from home. At the end of the day I believe the men that are playing will be great and will win the gold for our country."
Lowry made the decision to skip the tournament after meeting with his surgeon to evaluate the recovery of his thumb, which was operated on last month. The guard hoped to return to the court with the U.S. squad this week when they resume practices in California.
Bagley was a member of the younger Select Team before earning a promotion to the U.S. national team Friday night.
After the departure of Lowry and Bagley, the national team has 15 players remaining on the roster, which must be trimmed down to 12 before the beginning of the tournament.
The Americans will practice at the Los Angeles Lakers' facility this week before facing Spain in an exhibition game Friday night in Anaheim, Calif.