That's what Admiral Mike Mullen told the Senate today. From the Times:
The United States has long said that the ISI has close links to Afghan insurgents, particularly the Haqqani network, but no one has been as blunt as Admiral Mullen. He is to retire at the end of this month.
Coming from Admiral Mullen, the statements carried exceptional weight. He has been the American military official who has led the effort for years to improve cooperation with the Pakistanis.
Mullen had stern words for Pakistan, saying "By exporting violence, they’ve eroded their internal security and their position in the region. They have undermined their international credibility and threatened their economic well-being."
The September 10 attack, carried out via a cargo-truck bomb, killed at least five people and wounded 77. This week, former president Burhanuddin Rabbani was assassinated; no one has yet claimed credit (or officially placed blame).