US President Donald Trump has pledged a major upgrade to the country's nuclear deterrent, but are a handful of private defence contractors driving the multi-billion dollar modernisation programme?

Jonathan King, a veteran campaigner against nuclear proliferation and professor at MIT, argues guaranteed profit margins and secrecy make the industry very attractive to such companies.

But Hawk Carlisle, chief executive of the US National Defense Industrial Association, tells Ed Butler the private sector is the only area capable of building such weapons and that there is adequate competition and government scrutiny.

Plus, how complicated is it to make a bomb these days? Robert Kelley, a former weapons inspector in Iraq, says technology is advancing so fast that it's getting easier and easier.

Producer: Laurence Knight

(Picture: Ballistic missiles being launched in North Korea. Credit: AFP photo/KCNA via KNS, Getty Images)