Clinton and Chairman of U.S. Joint Chiefs of Staff Admiral Mike Mullen met President Asif Ali Zardari, Prime Minister Yusuf Raza Gilani as well as Army chief General Ashfaq Kayani in the highest profile visit since U.S. Navy SEALS killed the al Qaeda leader.

The discovery of the al Qaeda leader in a garrison town just 50 km away from the capital, Islamabad, on May 2 raised fresh doubts about Pakistan's reliability as a partner in the U.S.-led war on militancy.

Clinton has emphasized the need to continue working closely with Pakistan, but her visit to Islamabad, kept secret for security reasons, came as U.S. lawmakers questioned whether Pakistan should be receiving billions of dollars in aid.

"They have cooperated; we have always wanted more," a U.S. official told reporters traveling on Clinton's plane ahead of the surprise visit.

Reuters