Senate Republicans are urging President Barack Obama not to make recess appointments to the National Labor Relations Board.
All 47 GOP senators are warning Obama in a letter that bypassing the Senate would set a dangerous precedent. The board has been a target of Republicans who say it has acted too favorably toward unions.
Last week, Obama nominated Deputy Labor Secretary Sharon Block and union lawyer Richard Griffin to fill two vacancies on the board.
The board usually has five members but has been operating with just three. It will lose another member soon, leaving it without power to make any major decisions.
Union leaders have urged Obama to fill the seats. But South Carolina Republican Sen. Lindsey Graham has vowed to block any appointments through the Senate confirmation process.