(Reuters) — President Barack Obama on Tuesday nominated two corporate attorneys to serve on the National Labor Relations Board and renominated its current chairman amid uncertainty about the board's authority created by a federal appeals court ruling.

The nominations come as Congress is considering Republican-backed measures that would effectively pause the NLRB's work until its ability to conduct official business is confirmed by the U.S. Supreme Court or the Senate.

In addition to Chairman Mark Gaston Pearce, whose current term ends in August, Prsident Obama said he was naming Harry Johnson and Philip Miscimarra to the NLRB. The two are both employment attorneys who represent companies, balancing the board's three existing members, who have union or Democratic backgrounds.

"I urge the Senate to confirm them swiftly so that this bipartisan board can continue its important work on behalf of the American people," President Obama said in a statement on Tuesday.

It is not clear how the Senate will react to the nominations when they come up in that chamber for confirmation. The Senate now has five board nominations to consider, after President Obama in February asked the chamber to confirm existing members Sharon Block and Richard Griffin.

President Obama had named Ms. Block and Mr. Griffin to the NLRB in January 2012 as recess appointments — a tactic that does not require confirmation since it is used when the Senate is in recess. But the District of Columbia Circuit Court ruled in January that the appointments were invalid because the Senate was not actually recessed at the time the nominations were made.

%%BREAK%%

Sen. Lamar Alexander, R-Tenn., who introduced a budget amendment last month that would defund decisions and regulations made by the NLRB since the recess appointments, welcomed the nominations of Messrs. Johnson and Miscimarra but at the same time urged Ms. Block and Mr. Griffin to step down from the board.

"As tradition requires, the president has properly nominated two Republicans to serve on the National Labor Relations Board," Sen. Alexander said in a statement. "It is now the Senate's role to exercise advice and consent on the nominees."

Legislation also is pending in the House of Representatives that would prevent the NLRB from taking any official action until it has a Senate-confirmed quorum or the Supreme Court rules on the existing board's validity. That bill is the subject of a House Rules Committee hearing set for Wednesday.

The NLRB, an independent federal agency that oversees union elections and polices unfair labor practices, needs a quorum of three of its five board members in order to make decisions and take other actions. Its members serve staggered five-year terms.

There are questions about whether the NLRB had a valid quorum when it made more than 600 decisions following the appointment of Ms. Block and Mr. Griffin in January 2012, given there are two additional vacancies. At least 35 cases involving the board are now on hold in the D.C. Circuit while the board appeals the case.

Challenges to the NLRB's authority have been made in at least 73 cases pending in federal appeals courts, according to records kept by the board.

%%BREAK%%

Labor leaders said their primary goal is ensuring the board's functions, even if two of the nominees are considered pro-management.

"The package includes individuals who have challenged recent actions by the NLRB and who have views on labor relations matters that we do not agree with. But working people need and deserve a functioning NLRB," AFL-CIO President Richard Trumka said in a statement.

Mr. Miscimarra, a partner at the Chicago law firm Morgan, Lewis and Bockius L.L.P., has represented management in employment disputes, including helping business groups weigh in on cases that impact labor and employment policy. He has represented the U.S. Chamber of Commerce, one of the board's most reliable critics, in cases that challenged the rules governing union elections and employee involvement initiatives.

As a longtime senior fellow at the University of Pennsylvania's Wharton School of Business, Mr. Miscimarra has focused the majority of his research on the National Labor Relations Act, the statute that created the board.

Mr. Johnson also specializes in management-side labor and employment cases as a partner at Arent Fox L.L.P. in Los Angeles.

Mr. Pearce has been the board's chairman since August 2011 and a member of the NLRB since March 2010. He was a partner at the law firm Creighton, Pearce, Johnsen & Giroux from 2002 to 2010, where he represented unions. His next term would end in 2018.

Ms. Block is a former labor counsel to Sen. Edward Kennedy, and Mr. Griffin is a former general counsel for the International Union of Operating Engineers.