Belgian Defence Minister Theo Francken said the US and Nato were faced with a “marriage crisis” as frustrations mount on both sides of the Atlantic, urging Washington to stand with its allies or risk America’s fall.

Francken, speaking at a think tank event in Washington on Tuesday, likened the strained transatlantic relationship, which has held for close to 80 years, to a “crisis”, saying “it’s very difficult”.

“I’m convinced that we’re having a marriage crisis … There’s a lot of frustration on...