J. Scott Applewhite, Associated Press
In this March 14, 2013, file photo, Rob Nabors, President Barack Obama's deputy chief of staff, leaves a closed-door meeting between Obama and Senate Republicans, at the Capitol in Washington. Nabors would be assigned to oversee a review of the VA health care system after allegations of delayed care.

PHOENIX — A top adviser to President Barack Obama is headed to Phoenix to meet with staff at the Veterans Affairs office as the beleaguered agency grapples with allegations of treatment delays and preventable deaths, the White House announced Tuesday.

The move comes as pressure mounts on Capitol Hill for an overhaul of the VA and a change in leadership to restore accountability at the agency.

Obama announced last week that White House Deputy Chief of Staff Rob Nabors would be assigned to oversee a review of the VA health care system after allegations of delayed care that may have led to patient deaths and a cover-up by top administrators in Phoenix.

Similar claims have been reported at VA facilities in Pennsylvania, Wyoming, Georgia, Missouri, Texas, Florida and elsewhere.

Nabors planned to meet Tuesday in Washington with representatives of several veterans' organizations, including the American Legion and Disabled American Veterans, among others.

He will meet Thursday with leadership at the Phoenix Veterans Affairs Medical Center, including with interim director Steve Young, said White House spokesman Jay Carney.

The current director of the Phoenix VA Health Care System, Sharon Helman, has been placed on leave indefinitely while the Inspector General's Office investigates the claims raised by several former VA employees.

A former clinic director for the VA in Phoenix first came out publicly with the allegations in April. Dr. Samuel Foote, who retired in December after nearly 25 years with the VA, says that up to 40 veterans may have died while awaiting treatment at the Phoenix hospital and that staff, at the instruction of administrators, kept a secret list of patients waiting for appointments to hide delays in care.

Investigators probing the claims say they have so far not linked any patient deaths in Phoenix to delayed care.

The allegations have sparked a firestorm on Capitol Hill and some calls for VA Secretary Eric Shinseki's resignation. The VA's undersecretary for health care, Robert Petzel, has since stepped down amid the ongoing probe.

However, Republicans denounced the move as a hollow gesture, given Petzel had already been scheduled to retire soon. Rep. Jeff Miller, R-Fla., chairman of the House Veterans' Affairs Committee, called the announcement "the pinnacle of disingenuous political doublespeak."

Republican Sen. Jerry Moran of Kansas, a member of the Senate Veterans Affairs Committee, told The Associated Press on Tuesday he plans to introduce legislation this week to ensure that internal probes by the VA's Office of Medical Inspector are released to Congress and the public "so the full scope of the VA's dysfunction cannot be disguised."

Moran noted that a VA nurse in Cheyenne, Wyoming, was put on leave this month for allegedly telling employees to falsify appointment records. The action came after an email about possible wait-list manipulation at the Cheyenne hospital was leaked to the news media.

But Moran said the Cheyenne center was already the subject of a December 2013 report by Office of the Medical Inspector. That report apparently substantiated claims of improper scheduling practices, but it is unclear if action taken at the Cheyenne center was based on the medical inspector's findings, Moran said.

"Because OMI reports are not available to the public and have not been previously released to Congress, it is impossible to know whether the VA has taken action to implement the OMI's recommendations for improvement in each case," Moran said.

Meanwhile, Sen. John Cornyn, the No. 2 Republican in the Senate, called on Obama to back off plans to nominate Jeffrey Murawsky to replace Petzel at the VA.

Murawsky, a career VA administrator, directly supervised Helman from 2010 to 2012.

"Instead of nominating a reformer from outside the VA system who can bring fresh leadership, you have appointed Dr. Jeffrey A. Murawsky, a career administrator whose own tenure at the VA raises serious concerns," Cornyn told Obama in a letter Tuesday.

The White House has said Obama remains confident in Shinseki's leadership and is standing behind Murawsky's nomination.

Daly reported from Washington. AP staff writers Donna Cassata and Darlene Superville in Washington contributed to this report.