Agency officials said that tracking Mr. bin Laden and his deputies remained a high priority, and that the decision to disband the unit was not a sign that the effort had slackened. Instead, the officials said, it reflects a belief that the agency can better deal with high-level threats by focusing on regional trends rather than on specific organizations or individuals.

"The efforts to find Osama bin Laden are as strong as ever," said Jennifer Millerwise Dyck, a C.I.A. spokeswoman. "This is an agile agency, and the decision was made to ensure greater reach and focus."

The decision to close the unit was first reported Monday by National Public Radio.

Michael Scheuer, a former senior C.I.A. official who was the first head of the unit, said the move reflected a view within the agency that Mr. bin Laden was no longer the threat he once was.

Mr. Scheuer said that view was mistaken.

"This will clearly denigrate our operations against Al Qaeda," he said. "These days at the agency, bin Laden and Al Qaeda appear to be treated merely as first among equals."

In recent years, the war in Iraq has stretched the resources of the intelligence agencies and the Pentagon, generating new priorities for American officials. For instance, much of the military's counterterrorism units, like the Army's Delta Force, had been redirected from the hunt for Mr. bin Laden to the search for Abu Musab al-Zarqawi, who was killed last month in Iraq.