Pakistan says it has a senior al Qaeda leader who had been ordered by Osama bin Laden to hit United States, European and Australian economic targets.
Pakistan's military is describing the capture of Younis al-Mauritani as another fatal blow to al Qaeda.
Two other senior operatives from the militant group have also been detained. No further details were provided.
The United States helped Pakistan's Inter-Services Intelligence (ISI) spy agency conduct the arrests, the military said.
A US official said his country provided critical information and technical help in the operation and the White House said the capture was an example of counterterrorism co-operation.
Pakistan has been under intense pressure from its ally the United States to crack down harder on al Qaeda and other militant groups since US special forces found Osama bin Laden in a Pakistani town in May and killed him in a secret raid.
US officials have said al Qaeda's deputy chief, Libyan national Atiyah abd al-Rahman, was killed in a US drone strike in Pakistan near the Afghan border on 22 August. Pakistan officials have not confirmed his death.
