Bilateral ties between the United States and Pakistan are under scrutiny after U.S. forces stormed a fortified compound near an elite Pakistani military academy and killed al-Qaida leader Osama bin Laden.
Bin Laden was believed to have slipped into Pakistan from Afghanistan after a raid on his compound in Tora Bora in 2001.
U.S. Sen. Dick Lugar, R-Ind., ranking member of the Senate Foreign Relations Committee, expressed concern over Washington's support of Islamabad in the wake of the bin Laden raid in Pakistan.
Lugar said the billions of dollars of military aid for Pakistan comes with a requirement that Islamabad is doing its part in the fight against terrorist groups like al-Qaida. So far, he said, that remains an open question.
"Pakistanis must recognize that the United States does not give out blank checks," he said.
U.S. Sen. John Kerry, D-Mass., chairman of the Senate committee and Washington's point man on Pakistani relations, said after returning from a trip to the region that it was time for "to recalibrate, to readjust, to tweak and to use this opportunity to push a reset button as we go forward."