WASHINGTON, Nov. 13 — Just four days after Michael B. Mukasey was sworn in as attorney general, Justice Department officials said Tuesday that President Bush had reversed course and approved long-denied security clearances for the Justice Department’s ethics office to investigate the National Security Agency’s warrantless surveillance program. The department’s inspector general has been investigating the department’s involvement with the N.S.A. program for about a year, but the move suggested both that Mr. Mukasey wanted to remedy what many in Congress saw as an improper decision by the president to block the clearances and that the White House chose to back him.

Tony Fratto, a White House spokesman, and Brian Roehrkasse, a Justice Department spokesman, declined to say whether Mr. Mukasey had pressed Mr. Bush on the clearances for the department’s Office of Professional Responsibility. Mr. Mukasey himself had indicated in a written answer to senators on Oct. 30, before his confirmation, that the clearance issue had been resolved. But Democrats said they thought Mr. Mukasey deserved credit.

“It seems the new attorney general understands that his responsibility is to the American people and the rule of law and not to any particular person, including the president,” said Representative Maurice D. Hinchey, Democrat of New York, who had first demanded the internal Justice Department investigation.

In response to appeals from Mr. Hinchey and other members of Congress, the head of the Office of Professional Responsibility, H. Marshall Jarrett, said in February 2006 that he had opened an investigation of the conduct of department lawyers in approving and overseeing the N.S.A. program. But three months later he said the inquiry had been dropped because his staff had been denied the necessary high-level clearances.