One of the most senior intelligence officers in the CIA's Osama bin Laden unit said yesterday that fewer experienced officers are assigned to defeating the al Qaeda leader and his followers now than there were on Sept. 11, 2001.

Michael Scheuer, the author of a best-selling book critical of the agency's fight against terrorism, said that even though the number of officers assigned to the task has increased substantially, "the level of experienced officers is a little less since September 11."

More than 50 percent of those working on terrorism and against bin Laden are assigned to the job temporarily, for 30 to 90 days at a time, he said. "Sometimes more is just more," said Scheuer, whose superiors have forbidden him to speak to the media.

Some of the most experienced officers have been assigned to Iraq, or sent to the FBI or the Department of Homeland Security's new terrorist threat information center, the 22-year career officer said. As a result, he said, the CIA "has diluted the pool that supports our people overseas," and because of that, "in the long term, we're less safe than we should be."

Scheuer said he agreed to be interviewed because the Atlantic Monthly had posted on its Web site a letter he wrote to the Senate Select Committee on Intelligence that offers a detailed critique of the CIA's counterterrorism efforts. Scheuer, who has worked on counterterrorism since 1992, said he sent his superiors an e-mail Saturday morning explaining that he intended to answer media queries about the letter but received no response.

"I'm not disgruntled," he said. "It's been a great place to work. [But] . . . I don't think we're doing the right thing" to defeat terrorists. . . . We have to put some of our best people on it, and have them stay for a long time."

A CIA representative, speaking on the condition of anonymity, disputed Scheuer's assessment.

"His assertions are off the mark," she said. "There are more officers working against al Qaeda both at CIA headquarters and overseas than prior to 9/11. Our knowledge and substantive experience on al Qaeda has increased enormously since 9/11."

She said that the size of the CIA's counterterrorism center had "more than doubled" since the Sept. 11 attacks and that "its analytic capability has dramatically increased."

The CIA allowed Scheuer to publish his book, "Imperial Hubris," anonymously, and to conduct media interviews to promote it. He became a critic of the war in Iraq, saying it inflamed anti-American sentiment among Muslims. Eventually his name was published.

Some White House officials and pundits asserted that the CIA had allowed Scheuer to act as its surrogate critic on the war. In July, CIA officials forbade Scheuer to speak publicly.

Scheuer said he believes that the agency silenced him after CIA officials realized he was blaming the CIA, not the administration, for mishandling terrorism. "As long as the book was being used to bash the president, they gave me carte blanche to talk to the media," he said. "But this is a story about the failure of the bureaucracy to support policymakers."