Beleaguered Veterans Secretary Eric Shinseki has stepped down after being summoned to meet President Barack Obama at the Oval Office.
Mr Obama said he had decided to accept Mr Shinseki's resignation with "considerable regret".
Friday morning's Oval Office meeting came as pressure built on Mr Shinseki to hand in his resignation over the healthcare scandal engulfing the Veterans Affairs agency.
Mr Obama told ABC News beforehand that he planned to have a "serious conversation" with Mr Shinseki about his "capacity" to do the job.
Claims surfacing last month that up to 40 veterans may have died while awaiting treatment in the Arizona healthcare system have spawned a nationwide inquiry.
Earlier on Friday morning, Mr Shinseki, a retired four-star general, apologised and said he would oust the leadership at the Phoenix hospital at the centre of the affair.
Republican and Democratic lawmakers had demanded he quit over the controversy, which has become a political timebomb.
But Mr Shinseki gave no sign that he would step down as he appeared at a conference for homeless veterans in Washington DC earlier on Friday.
He told the event: "We now know that VA has a systemic, totally unacceptable lack of integrity within some of our veterans health facilities.
"That breach of integrity is irresponsible, it is indefensible and unacceptable to me."
Mr Shinseki, who has led the agency for five years, also said he had been "too trusting" in being led to believe that the issues were not so severe.
"Given the facts I now know, I apologise as the senior leader of Veterans Affairs," he said, adding that the problems could be fixed.
An interim report found this week that up to 1,700 military veterans were "at risk of being lost or forgotten" after being kept off waiting lists amid "significant delays" at the Phoenix clinic.
The Veterans Affairs (VA) inspector general, which is investigating 26 facilities run by the agency nationwide, said medical-care delays were "systemic throughout".
The government-run system provides medical care to about 6.5 million US veterans annually.
Original headline: Obama's Veterans Secretary Resigns
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