Federal prosecutors released paperwork Wednesday. They can delay until June 21 deciding how to proceed with charges in the May 1 attempted bombing of Times Square.
The Pakistan-born U.S. citizen was arrested two days after a vehicle was found with a large bomb that failed to ignite.
Authorities say he cooperated with investigators for two weeks before he asked for a lawyer. Shahzad was charged with attempted use of weapons of mass destruction and attempted acts of terrorism.
A message for comment left with his lawyer was not immediately returned.