National Counterterrorism Center Director Michael Leiter testifies on Capitol Hill on Sept. 22. (Manuel Balce Ceneta/AP)

The director of the National Counterterrorism Center plans to resign next month, White House officials announced Thursday, adding to the turmoil at the top levels of President Obama’s national security team.

Michael E. Leiter has been credited with overseeing the center’s emergence as a key component of the U.S. intelligence community, combing through thousands of threat reports each month for clues to looming terrorist plots.

But Leiter’s tenure co­incided with adaptations by al-Qaeda and a flurry of smaller-scale plots against U.S. targets that at times appeared to catch the NCTC, as the center is known, off guard.

Obama praised Leiter in a statement issued by the White House on Thursday, calling him “a trusted adviser to me and to the entire national security team, providing us with an in-depth understanding of terrorist activities that affect our nation’s security.”

The White House did not signal whether it had identified a possible replacement.

Leiter had been in the job for nearly four years, making him one of the highest-ranking holdovers from the George W. Bush administration.

Over the past year, Leiter has led efforts to call attention to the threat posed by affiliates of al-Qaeda, including its offshoot in Yemen. In congressional testimony this year, he called al-Qaeda in the Arabian Peninsula “probably the most significant risk to the U.S. homeland.”

AQAP, as the Yemen-based group is known, has been linked to a series of near-miss plots, including the attempted bombing of a Detroit-bound airliner on Christmas 2009.

The NCTC was faulted last year for breakdowns leading to that unsuccessful attack, including the failure to place the would-be bomber on aviation watch-lists despite warnings that had come to the CIA’s attention.

Leiter instituted a series of changes after that attack to improve the NCTC’s ability to monitor plots.

An NCTC official said that Leiter, who recently remarried, has not accepted another position, and is resigning because he thought that he had spent enough time in the job. News of his planned departure comes just weeks after al-Qaeda leader Osama bin Laden was killed in a U.S. military raid.

Andrew M. Liepman, who was recently appointed deputy director of the NCTC, will serve as acting chief until a replacement is named.