WASHINGTON - The FBI owes it to the victims of the San Bernardino terror attack to do what it can to gain access to the locked cellphone used by one of the gunmen, FBI Director James Comey said Sunday night.

In a statement posted on the Lawfare blog, Comey sought to defend the FBI demand for access to the phone as well as counter arguments from Apple Inc. that its court fight with the company risks threatening the digital privacy of Apple customers all over the world.

"We simply want the chance, with a search warrant, to try to guess the terrorist's passcode without the phone essentially self-destructing and without it taking a decade to guess correctly. That's it," Comey wrote in a four-paragraph statement. "We don't want to break anyone's encryption or set a master key loose on the land."

The iPhone used by Syed Farook, who along with his wife killed 14 people in the December 2 rampage, may or may not hold clues to finding more terrorists, Comey wrote.

"But," he added "we can't look the survivors in the eye, or ourselves in the mirror, if we don't follow this lead."

The statement continues the verbal back-and-forth between Apple and the Justice Department that surfaced last Tuesday, when a magistrate judge in California directed Apple to help the FBI hack into the password-protected phone. The judge's order directs Apple to create specialized software that could be loaded onto the phone to bypass a self-destruct feature that erases all data after 10 consecutive, unsuccessful attempts to guess the unlocking passcode. That way, the FBI could use technology to rapidly and repeatedly test numbers in what's known as a brute force attack.

Apple's chief executive, Tim Cook, has strongly objected to the government's request, and the company is expected to file its opposition in court this week.

Comey did acknowledge in his statement that the clash has laid bare a tension between privacy and security. But he said that divide should not be resolved by the FBI nor "corporations that sell stuff for a living."

"It should be resolved by the American people deciding how we want to govern ourselves in a world we have never seen before," he said.