Clinton, Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, and Marine Corps Gen. John R. Allen, commander of the International Security Assistance Force and of U.S. Forces Afghanistan, each called their Pakistani counterparts, the Pentagon spokesman said.
Cameron P. Munter, U.S. ambassador to Pakistan, also met with Pakistani government officials in Islamabad.
From Kabul, Allen sent his "most sincere and personal heartfelt condolences ... to the families and loved ones of any members of Pakistan Security Forces who may have been killed or injured."
The incident, he added, "has my highest personal attention and my commitment to thoroughly investigate it to determine the facts."
In its statement, ISAF said its leadership remains committed to improving security relations with Pakistan, including coordination of operations along border regions in the united fight against terrorism.
Clinton and Panetta each expressed their sympathies and a commitment to review the circumstances of the incident, Kirby said, noting that both stressed "the importance of the U.S.-Pakistani partnership, which serves the mutual interests of our people."
All the leaders, he added, pledged to stay in close contact with their Pakistani counterparts as both nations work through this challenging time.