'Bunker Buster' even bigger than MOAB

A weapons expert says the US has a more powerful bomb than the Massive Ordnance Air Blast, which is now "moving down the tracks".

Dr Martin Navias, from the Centre for Defence Studies at King's College London, told Radio 4's The World at One that the Massive Ordnance Penetrator - known as the "bunker buster" - is the weapon the Americans would want to use against North Korea.