U.S. President George W. Bush warned North Korea last year against transferring nuclear material to Syria, Iran or a terrorist organization, saying such a move would be perceived as a "grave threat," a former U.S. official recently told Haaretz.

In a telephone conversation, the former U.S. ambassador to the UN, John Bolton, said North Korea may be using Syria and Iran as "safe havens" for its nuclear activity.

Bolton, now affiliated with the "American Enterprise Institute" in Washington, served Bush in his first term as Under-Secretary of State for Arms Control and International Security. In that capacity, as well as later, he clashed with other officials, most notably from CIA, regarding Syria's nuclear plans.