Al-Qaida leaders directed Padilla to blow up an apartment building and set fire to a hotel or gas station.
According to a New York Times report, a U.S. assessment of Khalid Sheikh Mohammed, the alleged mastermind of the 9/11 attacks, was posted on WikiLeaks and described an early 2002 meeting with Padilla. The file says Mohammed directed Padilla to rent an apartment in Chicago and "initiate a natural gas explosion to cause the building to collapse." Mohammed also told Padilla to "study the feasibility" of setting fire to a hotel or gas station, the assessment says.
Padilla was arrested back in 2002 after he arrived at O'Hare Airport from Pakistan. At the time, officials suspected he planned to set off a dirty bomb.
Padilla was later found guilty of conspiring to kill people overseas.
The classified military files obtained by the WikiLeaks website also revealed other potential al-Qaida plots against the United States, including post-9/11 aircraft attacks on the West Coast, The New York Times reported Monday.
The schemes -- none of which were executed -- are described in U.S. military assessments of terrorism suspects being held at the military prison at Guantanamo Bay, Cuba. Those detainees include Khalid Sheikh Mohammed, the alleged mastermind of the 9/11 attacks.
One of the dossiers described by the Times concerns Saifullah Paracha, a New York travel agent for years who allegedly worked with Mohammed on plots to follow up on the attacks of Sept. 11, 2001. One plan suggested by Paracha involved smuggling plastic explosives in shipments of clothing bound for the U.S., the Times reported.
The Mohammed file also includes discussions of plots to hijack cargo planes, hack into bank computers and cut the cables holding up the Brooklyn Bridge.
The Times said the assessments were obtained last year by WikiLeaks but provided to the newspaper by another source.
The Defense Department on Monday condemned the release of information from the classified documents, which it said were written between 2002 and early 2009 and "based on a range of information available then." The leaked files "may or may not represent the current view of a given detainee," the Pentagon said.
White House Press Secretary Jay Carney echoed that statement, telling reporters Monday that "a detainee assessment brief in 2006 may or may not be reflective of the administration or the government's view of that particular detainee in 2011."
(The Associated Press contributed to this report.)