U.S. military officials have for years talked of links between Pakistan's spy agency and militant groups attacking American targets across the border in Afghanistan.
During a hearing Thursday on Capitol Hill, the top U.S. military officer said there's proof.
The chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, was blunt. Supported by Pakistan's Inter-Services Intelligence (ISI) agency, the militant Haqqani network was responsible for attacks that included the one on the U.S. Embassy in Kabul last week, he said.
"We also have credible intelligence that they were behind the June 28 attack on the Inter-Continental Hotel in Kabul and a host of other, smaller but effective operations," he told the Senate Armed Services Committee hearing on U.S. strategy in Afghanistan and Iraq.
This was Mullen's last appearance before Congress before retiring at the end of this month. The chairman is known for taking a diplomatic approach with Pakistan, but after last week's attack on the U.S. Embassy, Mullen issued an unusually stern warning.
"In choosing to use violent extremism as an instrument of policy, the government of Pakistan — and most especially the Pakistani army and ISI — jeopardizes not only the prospect of our strategic partnership, but Pakistan's opportunity to be a respected nation with legitimate regional influence," he said.
Still Providing Safe Haven
Mullen has been the Obama administration's key link between the U.S. and Pakistan, visiting that country dozens of times for personal meetings with the head of Pakistan's military.
"I've done it because I believe that a flawed and difficult relationship is better than no relationship at all. Some may argue I have wasted my time, that Pakistan is no closer to us than before and may now have drifted even further away. I disagree," he said.
Mullen said cooperation with Pakistan has been getting better, especially the fight against al-Qaida. For example, earlier this month, Pakistan arrested the group's operations chief.
But both Mullen and Defense Secretary Leon Panetta said Pakistan is still harboring other terrorist groups, like the Haqqanis.
"We cannot tolerate their having these kind of safe havens. We cannot tolerate having terrorists coming across the border, attacking our forces, killing our soldiers and then escaping back into that safe haven. That is not tolerable," Panetta said.
Calls For Change
Some senators are losing patience after 10 years of war.
"We should get out as quickly as we can," said Democrat Joe Manchin of West Virginia. "Go and fight terrorism anywhere and everywhere to keep it from the shores of America, but I do not believe we can win and change the Afghans or the Pakistanis."
The secretary of defense responded.
"I understand there's been waste, I understand that mistakes have been made," Panetta said. "But I also believe that this is a point where the U.S. has got to stick with it and not just walk away, largely because the last thing we should do is to say to those families who have lost loved ones that somehow all of this was in vain."
At the same time, Panetta said the U.S. must find a way to get Pakistan to stop reaching out to the U.S. with one hand and propping up terrorist groups with the other.
"Would you agree with me," asked Republican Sen. Lindsey Graham of South Carolina, "if something doesn't change in Pakistan substantially that we are on a collision course with Pakistan?"
"It has to change," Panetta responded. "We can't continue the situation as it is now."
Panetta said he has made it clear to Pakistan that the U.S. will do everything in its power to protect American forces from attacks that originate from Pakistan. He refused to say exactly what that could entail.