A defiant Chrysler is refusing a government request to recall about 2.7 million SUVs to fix fuel tanks that could leak and cause fires in rear-end collisions. Chrysler said Tuesday that the National Highway Traffic Safety Administration has asked in a letter that the company recall Jeep Grand Cherokees from 1993 through 2004 and Jeep Libertys from 2002 through 2007. Such a refusal by an auto company is rare. It was unclear how NHTSA would respond. Messages were left for an agency spokeswoman.