According to previously secret US documents posted by the National Security Archive, the United States government warned Taliban leader Mullah Omar in a private message that 'every pillar of the Taliban regime will be destroyed'.

The formerly secret documents detail how the day after 9/11, Deputy Secretary Armitage presents a "stark choice" to Pakistani Intelligence (ISI) Chief Mahmoud Ahmed, "Pakistan must either stand with the United States in its fight against terrorism or stand against us. There was no maneuvering room."

A memo on US strategy from Donald Rumsfeld to President Bush dated September 30, 2001, says, "If the war does not significantly change the world's political map, the U.S. will not achieve its aim/ There is value in being clear on the order of magnitude of the necessary change. The USG [U.S. Government] should envision a goal along these lines: New regimes in Afghanistan and another key State (or two) that supports terrorism."

The National Security Council's October 16, 2001, strategic outline of White House objectives to destroy the Taliban and al-Qaeda while avoiding excessive nation-building or reconstruction efforts. "The U.S. should not commit to any post-Taliban military involvement since the US will be heavily engaged in the anti-terrorism effort worldwide." The document also notes the importance of "CIA teams and special forces in country operational detachments (A teams)" for anti-Taliban operations.

You can read the documents on the NSA's web site here