"It is true that she has indeed lost her voice," Simpson's publicist, Rob Shuter, told The Associated Press on Tuesday. "She's been ordered to rest. ... She can talk, she can croak out a few sentences. She sounds a little off, but, you know, she can't sing."
Simpson, 26, fell ill Friday and has "a strain, a bruise on her vocal cord," Shuter told the AP.
The singer canceled an appearance on CBS' "Late Show With David Letterman" this week but dropped by MTV's "Total Request Live" on Tuesday to promote the album. Simpson, speaking in a hoarse voice, introduced music videos. She also signed CDs for fans.
Simpson hopes her condition improves by Friday, when she is scheduled to perform on NBC's "Today" show, Shuter said.
"She's trying," he said. "Everybody is hoping and keeping their fingers crossed."