WASHINGTON -- Senate Democrats have delayed a confirmation vote on Labor Secretary nominee Thomas Perez after Republicans threatened to use a separate hearing to criticize his handling of a whistleblower case.

A vote in the Senate Health, Education, Labor and Pensions Committee set for Thursday has been pushed back to May 8.

Committee Chairman Tom Harkin of Iowa was concerned Republicans would use the separate hearing as a forum to attack Perez in his absence. Harkin canceled the hearing on federal whistleblower laws, which also was set for Thursday.

Republicans have criticized Perez for declining to intervene in a whistleblower case against St. Paul, Minn., while he headed the Justice Department's Civil Rights Division. Perez made the decision as part of a deal in which the city agreed to withdraw another case from the Supreme Court that could have threatened the Justice Department's strategy in bringing housing discrimination cases.

Republicans claim Perez made the deal based on political ideology and not the merits of the whistleblower case, which could have won nearly $200 million for taxpayers. Perez has said the deal was in the best interest of the nation and was made only after receiving approval from senior Justice officials.

Senate Republicans had asked Harkin earlier this week to postpone the committee vote, saying they needed more time to examine the deal. Harkin initially refused the request but changed his mind. The change of heart occurred after Republicans planned to have Frederick Newell, the plaintiff in the whistleblower case, testify about weaknesses in whistleblower laws at the Occupational Safety and Health Commission.

"While I continue to believe there are no impediments to Mr. Perez's confirmation, I am agreeing to postpone his committee vote until May 8 in order to allow those senators who have asked the time to request additional information they believe they need and to evaluate his qualifications," Harkin said.

Tennessee Sen. Lamar Alexander, the committee's top Republican, said the delay was appropriate "so that senators could get responses to a number of outstanding questions as we evaluate this nominee."