The terrorist who orchestrated the 9/11 attacks views immigration as al Qaeda’s deadliest weapon against the U.S., according to a new book.

The Washington Examiner reported Wednesday that Khalid Sheikh Mohammad's strategy is detailed in “Enhanced Interrogation,” an upcoming book authored by CIA contractor James Mitchell. Mitchell’s work details his interrogation of multiple high-level extremists, including Mohammad, at the Guantánamo Bay detention center, the Examiner said.

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According to the book, Mohammad envisions a long game in which radical Islamists enter the U.S. and gradually destroy it using the legal system.

“From his perspective, the long war for Islamic domination wasn’t going to be won in the streets with bombs and bullets and bloodshed,” Mitchell says of Mohammad in his book. "No, it would be won in the minds of the American people.

“[Mohammad] said the terror attacks were good, but the ‘practical’ way to defeat America was through immigration and by out-breeding non-Muslims. He said jihadi-minded brothers would immigrate into the United States, taking advantage of the welfare system to support themselves while they spread their jihadi message.

“They will wrap themselves in America’s rights and laws for protection, ratchet up acceptance of Sharia-law, and then, only when they were strong enough, rise up and violently impose Sharia from within. He said the brothers would relentlessly continue their attacks and the American people eventually would become so tired, so frightened and so weary of war they would just want it to end.”

Mitchell’s book is scheduled for release on Nov. 29.

The 9/11 Commission Report describes Mohammad as “the principle architect of the 9/11 attacks” on Sept. 11, 2001.

The series of four coordinated attacks in New York City, Arlington, Va., and Shanksville, Pa., killed 2,996 people and injured more than 6,000 others.