A former U.S. ambassador to the United Nations has expressed concern over nuclear collaboration between North Korea, Iran and Syria.

John Bolton has called for a stronger Proliferation Security Initiative (PSI) and a review of alternative measures on Iran including an air strike.

The PSI goal is to stop the trafficking of weapons of mass destruction and all related materials.

Speaking before the House Foreign Affairs Committee, Bolton said that North Korea and Iran have conducted joint research and joint experiments on ballistic missiles since 1998 at the least.

He said the two countries' missile development is not in the interest to launch weather satellites but to make a vehicle to carry nuclear warheads.

He said the Syrian Al Kibar nuclear reactor, which Israel destroyed in 2007, was modeled after North Korea's Yongbyon reactor. He says that Iran also took part in the Syrian reactor project.