President Barack Obama's under-fire Veterans Affairs Secretary Eric Shinseki resigned Friday, paying the price for an expanding scandal over failures in health care for America's retired warriors.

"Secretary Shinseki offered his resignation. With considerable regret, I accepted," a pained Obama said, bowing to political reality, and letting go a treasured colleague he often hailed as an "American hero."

The president said that an initial review by Shinseki, 71, had found that delays and other management failures in veterans' health care were not confined to one facility in Arizona, but were systemic and nationwide.

"As he told me this morning, the VA needs new leadership. He does not want to be a distraction," Obama said in a hurriedly arranged on-camera statement.

"My assessment is that unfortunately he is right."

Obama struck an authoritative pose, seeking to convey decisiveness and resolve in the eye of a widening political storm over the treatment of veterans.

"I said we wouldn't tolerate misconduct, and we will not. I said that we have to do better, and we will."

The scandal of delays of weeks and months for veterans waiting for health appointments struck close to home for the Obama administration.

The president made taking care of American soldiers who fought in Iraq and Afghanistan a centerpiece of his 2008 White House campaign.

The concern for the welfare of retired warriors is no doubt sincere among top administration officials. Obama's wife Michelle and Vice President Joe Biden's wife Jill often advocate for the rights of veterans.

But it also offered Obama political cover when he was effectively running as an anti-war candidate, fanning discontent over Iraq, but could not be seen to be unsympathetic to the US soldiers doing the fighting.

- 'No time for distractions' -

Shinseki's position had become untenable in recent hours, as lawmaker after lawmaker -- including many Democrats running for re-election in November -- called for him to quit.

Obama is notoriously loathe to fire members of his administration -- especially to appease baying packs of political opponents and journalists -- but appeared to conclude that Shinseki was in an impossible position.

"We don't have time for distractions. We need to fix the problem," Obama said.

The president announced that Shinseki's deputy, Sloan Gibson, would take over on an interim basis until a permanent replacement is found.

Obama appeared saddened by the resignation of his fellow Hawaiian, a four-star general wounded in Vietnam who the president said had never been scared to talk truth to power.

Shinseki is renowned for warning as Army Chief of Staff that an occupation of Iraq would require several hundred thousand troops -- angering key members of the Bush administration who were trying to minimize the potential costs of an invasion for political reasons.

Shinseki's departure came days after Obama promised troops in Afghanistan that their country would care for them when they come home, and a week before he travels to France and meets an earlier generation of veterans as he marks the 70th anniversary of the Normandy landings.

- 'Indefensible' -

Earlier Friday, Shinseki said in a speech that he took full responsibility for the failures.

"After Wednesday's release of an interim inspector general report, we now know that VA has a systemic, totally unacceptable lack of integrity within some of our veterans' health facilities," he admitted.

Shinseki said that when he first became aware of the problems with the waiting lists he had thought they were isolated cases, but that he had now discovered widespread failings.

"I can't explain the lack of integrity amongst some of the leaders of our health care facilities," he said.

"This is something I rarely encountered during 38 years in uniform. And so I will not defend it because it is indefensible. But I can take responsibility for it. And I do."

Shinseki apologized to all veterans who had been denied care and said he had begun procedures to sack managers at the agency's office in Phoenix, Arizona, where the scandal first came to light.

The inspector general found that 1,700 veterans in the Phoenix area alone had been kept off the main waiting list for primary care. Up to 40 patients are said to have died while waiting for treatment.

There was widespread support for Shinseki's resignation from Capitol Hill -- but Republicans quickly turned their scrutiny on Obama.

"Today's announcement really changes nothing," said Republican House Speaker John Boehner.

"We'll hold the president accountable until he makes things right."