Asked by Sen. Lindsey Graham, R-S.C., whether the United States and Pakistan are on a collision course if something doesn't change, Panetta said, "it has to change, we can't continue the situation that's there now."
Panetta declined to reveal what options the United States might have available to prevent the Haqqanis from conducting more attacks against U.S. forces, as he said last week, but said they would not be a surprise to Pakistan.
"I've made very clear," he said, "that we will do everything necessary to protect our forces. I haven't spelled that out to them, but I would be very surprised if they were surprised by what we did to fulfill that commitment.
Today's hearing was Panetta's first congressional appearance since becoming defense secretary in July. It is also Mullen's final appearance before his term as chairman of the Joint Chiefs of Staff ends next Friday.