Folk singer and anti-war protester Joan Baez has said she was prevented from performing for US troops in hospital.
Joan Baez is headlining this year's Cambridge Folk Festival
In an interview with the Washington Post, Baez said US officials would not let her take part in the Washington DC gig with fellow singer John Mellencamp.
"There might have been one, there might have been 50 [soldiers] that thought I was a traitor," she told the paper.
A spokesman for Walter Reed Medical Center told Rolling Stone.com Baez's appearance was "not in the agreement".
Baez, famous for her renditions of anti-Vietnam war songs including Blowin' in the Wind, is well-known for her views against the war in Iraq.
"Four days before the concert, I was not 'approved' by the Army to take part," she said in a letter published in the Washington Post on Wednesday.
The 66-year-old singer said she wished she had not declined invitations to perform for soldiers returning from Vietnam.
"I have always been an advocate for non-violence and I have stood as firmly against the Iraq war as I did the Vietnam war 40 years ago," she wrote.
"I realise 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."
She added that in the light of her decision to take part, it was "a strange irony" that she was not allowed to perform.
The Walter Reed spokesman, Steve Sanderson, said they had only received the request for Baez to take part two days before last week's concert.
"These additional requirements were not in the agreement/contract and would have required a modification," he told the Rolling Stone website.
The Department of Defense was not available for comment.
Mellencamp is also known for singing anti-war songs but told MSNBC News the concert was not about politics and he was "going down there and showing support for these kids who really don't make any policies and who basically are following orders".