Washington (CNN) - Interior Secretary Ken Salazar on Sunday said the Gulf of Mexico oil spill from a destroyed rig "potentially is catastrophic."
Salazar told CNN's "State of the Union" program, "I think we have to prepare for the worst."
He said later in the program that "It is indeed a massive oil spill."
Asked what happened, Salazar said there was a failure in the technology that is intended to prevent a so-called blowout.
"There is no doubt at all here that that what has happened is the blowout prevention mechanism at the bottom of the well ... is defective," Salazar said. "While there have been blowouts in the past, we have never seen anything that has been quite of this magnitude."
Watch: Salazar on the oil spill
The Obama administration has ordered inspections of "blowout preventers" on other Gulf rigs, Salazar said. He noted that BP, which operated the destroyed rig, is legally responsible for the spill and any resulting damage.
"So our job is to keep the boot on the neck of" BP to ensure it meets its obligations, Salazar said.
Updated: 10:11 a.m.