* Fresh reports of VA care delays, cover-ups frustrate lawmakers
* Senators, veterans debate Shinseki's ability to fix problems
* Former general faced challenges head-on in U.S. Army career
By David Lawder and David Alexander
WASHINGTON, May 14 (Reuters) - U.S. Veterans Affairs Secretary Eric Shinseki will be fighting for his career and veterans' confidence in his massive agency on Thursday when he testifies before a Senate committee about veterans who died while awaiting care.
But as more reports surface of alleged schemes to mask long wait times at VA hospitals and clinics, he will have a tougher time persuading lawmakers that he can fix the VA's problems.
While President Barack Obama has repeatedly voiced support for Shinseki, the political tide could quickly turn against the former four-star general if he fails to credibly show the Senate Veterans Affairs Committee that he was unaware of any cover-ups of appointment wait times.
"He needs to do the right thing and that's fix what's broken, own up to what he knows and get all the evidence out there," said Republican Senator Johnny Isakson, a committee member.
Congress' growing impatience with the VA's problems in delivering care and shrinking a massive backlog in disability claims was evident on Tuesday.
House Veterans Committee Chairman Jeff Miller, a Republican, asked Obama to establish a bipartisan commission to investigate care access for veterans, citing "disturbing silence from the White House and one excuse after another from VA" on the issue.
Missouri senators Roy Blunt, a Republican, and Claire McCaskill, a Democrat, asked the VA to investigate allegations by a St. Louis VA doctor about mental health care delays.
Blunt said such cases must be investigated immediately, or Congress "will see if somebody else will do it if the secretary for veterans affairs won't."
Senator Bernie Sanders, an independent who chairs the Veterans Affairs Committee, said he is concerned that the VA is being "politicized" despite serving millions of veterans well.
The most prominent care delay case has been in Phoenix, where former VA physician Sam Foote said wait times of up to 21 months for appointments were covered up. He said patients' names were put on a secret list before spots opened up on an official list that met the agency's shorter waiting time goals. At least 40 people died last year while waiting for care, he said.
"We have more demand for services than we can possibly supply," Foote said in an interview, adding that the region, like other Sunbelt communities, had attracted massive numbers of military retirees.
Probes into similar schemes have been reported at VA facilities in Cheyenne, Wyoming, Fort Collins, Colorado, and San Antonio and Austin, Texas.
Vicky Olson said on Friday that her husband, former Marine Michael Olson, collapsed and died in March from complications of hypertension, obesity and asthma while awaiting an appointment with a primary care doctor at a VA clinic in Phoenix.
She said the VA "just needs to be fixed" and that includes a change at the top.
Tom Tarantino, the chief policy officer for the Iraq and Afghanistan Veterans of America, said the scandal will likely worsen and he isn't sure whether Shinseki, who has led the agency for over five years, is the right person for the job.
"We need strong accountability at the VA because what's happening is that people are losing faith in the system," he added.
But those who know him say Shinseki has faced challenges head on throughout his 38-year military career, and his approach to the VA problems is no different.
A Hawaiian-born graduate of the U.S. Military Academy at West Point, he served in Vietnam and was wounded three times, including by a land mine that blew off part of his right foot. He fought to keep the Army from amputating the foot above the ankle and then resisted military pressure to retire from the service, rising to the rank of general and in 1999 became Army chief of staff. (Additional reporting by David Schwartz in Phoenix and David Morgan and Richard Cowan in Washington; Editing by Caren Bohan and Cynthia Osterman)