In a letter to The Washington Post published Wednesday, she said rocker John Mellencamp had asked her to perform with him last Friday and that she accepted his invitation.
"I have always been an advocate for nonviolence and I have stood as firmly against the Iraq war as I did the Vietnam War 40 years ago," she wrote. "I realize now that I might have contributed to a better welcome home for those soldiers fresh from Vietnam. Maybe that's why I didn't hesitate to accept the invitation to sing for those returning from Iraq and Afghanistan. In the end, four days before the concert, I was not 'approved' by the Army to take part. Strange irony."
Baez, 66, told the Post in a telephone interview Tuesday that she was not told why she was left off the program by the Army. "There might have been one, there might have been 50 (soldiers) that thought I was a traitor," she told the paper.
The Post reported that Walter Reed officials did not respond to requests for comment Tuesday, but that in an e-mailed statement published Monday on RollingStone.com, spokesman Steve Sanderson said the medical center received the request for participation by Baez just two days before the concert.
"These additional requirements were not in the agreement/contract and would have required a modification," Sanderson told the magazine's Web site.
Baez's manager, Mark Spector, told the Post that Mellencamp's management invited Baez to perform in March and handled all the arrangements. The Post said Mellencamp's manager, Randy Hoffman, did not return calls requesting comment and that Mellencamp's publicist said the singer was ill Tuesday and unavailable.
But Mellencamp earlier told RollingStone.com: "They didn't give me a reason why she couldn't come. We asked why and they said, 'She can't fit here, period.' "