TOKYO (AP) — U.S. Secretary of State John Kerry says it would be "diplomatic malpractice" not to test Iran's willingness to comply with international demands over its nuclear program.

Kerry's comments today in Tokyo are his first on the subject since Israeli Prime Minister Benjamin Netanyahu delivered a United Nations speech warning the U.S. and the West against trusting Iran.

Kerry says the U.S. would not take any Iranian offers at face value. He also says Iran will have to prove it's willing to come clean about its nuclear program.

The secretary says he does not believe Netanyahu was criticizing U.S. effort to engage Iran, but rather warning of the possibility that Iran and its new leader, President Hassan Rouhani, might not be serious. Kerry says the U.S. agrees with that assessment.