The new state secrets law is so broad that it's self-defeating and must be amended before it comes into force in December or it will have a chilling effect on free speech, according to U.S. national security and civil liberties expert Morton Halperin.

Halperin said in an interview Thursday in Tokyo that the legislation, passed by the Diet last December, is "far out of step with the rest of the world" and should be amended immediately to provide protections for journalists, other private citizens and government whistleblowers.

The law's penalties of up to 10 years in prison for revealing classified information, which applies to private citizens, including journalists, are "dangerous," and repealing them should be the government's highest priority, Halperin said.