The first lady welcomed to the White House some 20 mayors and local officials who are among dozens around the country participating in a Mayors Challenge to End Veteran Homelessness.
"This is a good news day," she said, noting that homelessness among veterans has dropped by 24 per cent over the past three years.
The first lady did not refer to the unfolding scandal over access to services at the Veterans Affairs Department. But she said it is a "moral outrage" that 58,000 veterans remain homeless, saying "even one homeless veteran is a shame."
"When a veteran comes home kissing the ground, it is unacceptable that he should ever have to sleep on it," she told an East Room audience of hundreds of state and local officials and advocates for veterans and the homeless.
Also speaking at the event was acting VA Secretary Sloan Gibson, who took over last week after VA Secretary Eric Shinseki resigned amid a furor over VA delays in seeing patients and allegations of falsified waiting lists at VA hospitals and clinics nationwide.
"We are moving immediately to get veterans off the waiting lists and into clinics and we're taking action to fix the systemic problems that allowed these unacceptable waits to occur," Gibson said.
He added that the administration has "proven we can reduce veterans' homelessness. Now, let's end it."
The Obama administration in 2010 set a goal of ending homelessness among veterans by the end of 2015.
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