U.S. Defense Secretary Leon Panetta said during a trip to Kabul that stabilization efforts in Afghanistan would remain difficult as long as militants had safe havens in neighboring Pakistan, and that Washington was "reaching the limits" of its patience with Islamabad.
Pakistani officials said the captured al Qaeda leader was Naamen Meziche, a French national of Algerian origin, who is believed to have links with militant groups based in Europe. Media reports say he may have played a role in the 9/11 attacks.
Meziche worked closely with another al Qaeda leader, Younis al-Mauritani, who was responsible for international operations, Pakistani officials said.
Mauritani was captured by Pakistani authorities in September last year.
Pakistan officials did not specify the time or location of the capture of Meziche, who they said was the ringleader of a group of 11 people who left Germany in 2009 to fight U.S.-led forces in Afghanistan.
U.S. officials often describe Pakistan as an unreliable partner in the war on militancy and demand tougher action against militant groups, especially those based in Pakistan's volatile tribal regions near the border with Afghanistan.
Pakistan says it will not allow any militant safe havens inside its territory, and that it will pursue its own strategy against militant groups.