A U.S. security expert says North Korea has the ability to put nuclear warheads onto its medium-range Rodong missiles and threaten its regional neighbors.

David Albright, who heads the Institute for Science and International Security in Washington, made the assessment during an interview with Reuters news agency Friday.

Albright said the North is regarded to have the ability to reduce the diameter of the warheads, so they will fit inside a reentry vehicle.

John Pike, director of an online think tank GlobalSecurity.org, agreed with Albright, saying that the North has had the capacity to put a nuclear weapon onto a medium-range ballistic missile for several years.

But U.S. intelligence officials say there is no evidence that Pyongyang has loaded any warheads onto its Rodong missiles, let alone has nuclear-armed Rodongs ready for launch.

Some officials believe Pyongyang has yet to meet the engineering challenge of arming a missile.