US PRESIDENT Donald Trump’s plan for a “more flexible” nuclear strategy which would involve building lower-yield nuclear bombs rang alarm bells around the world at the weekend.

The Pentagon’s Nuclear Posture Review, published on Friday, argues that the US should invest in smaller tactical nuclear missiles which could supposedly be used without triggering a global nuclear war.

Pentagon policy chief John Rood said the purpose would still be “deterrence,” but Defence Secretary James Mattis suggested the weapons could be used in response to a non-nuclear attack.