Donald Trump has declared that the US is going to withdraw from a key nuclear treaty with Russia. America says that they’ve broken the terms, Russia denies any wrongdoing.
As tensions rise between the two powers, there are fears this will lead to further erosion of important limitations for nuclear warfare.
So should we be concerned about an impending nuclear conflict?
The BBC’s Jonathan Marcus looks at what the potential consequences might be.
Video by Olivia Lace-Evans. Additional production by Laurence Peter.