The program is scheduled to air live at 8 p.m. EST Saturday on NBC, Telemundo, Pax and various cable channels.
Other stars announced Thursday for the benefit include Lucy Liu, Josh Groban, Jay Leno, Natalie Portman, Nicolette Sheridan and Naomi Watts.
Stevie Wonder, Meg Ryan, Clint Eastwood, Mary J. Blige and George Clooney were among previously announced participants.
Sony's Connect music store will offer downloads of live performances from the concert, with proceeds going to the American Red Cross International Response Fund (search).
SBC Communications is underwriting the two-hour, commercial-free benefit.
The tsunami, triggered by the world's most powerful earthquake in 40 years, has killed more than 157,000 people in Asia and Africa.