U.S. Secretary of Defense Robert Gates says countries that are not part of the Nuclear Nonproliferation Treaty are not exempt from U.S. nuclear retaliation.

Appearing on the CBS program "Face the Nation," Gates said all options are on the table regarding North Korea and Iran.

The Obama administration’s revised nuclear policy, announced last Tuesday, says that the U.S. will not use nuclear weapons to respond to a chemical or biological attack from a nonnuclear country.

But Gates says the new U.S. nuclear policy is “flexible,” should significant contingencies arise. He said that that if a nation develops biological weapons, thereby creating serious concerns, President Obama reserves the right to revise the policy.

He said that the policy dictates that any country using chemical or biological weapons against the U.S. will "suffer a devastating conventional retaliation."