US President Donald Trump met on Wednesday with members of the NATO alliance, an organisation he has consistently sought to influence over the years. His latest comments, casting doubt on the US commitment to mutual defence guarantees, have clearly rattled its members.

Trump's remarks en route to the Netherlands, stating his fidelity to Article 5 "depends on your definition," drew significant attention at the NATO summit. Also under scrutiny will be the new and fragile Iran-Israel ceasefire, which the Republican president helped broker after the US conducted airstrikes on Iran's nuclear facilities.

Simultaneously, the alliance is poised to enact one of Trump's chief priorities: a pledge by NATO member countries to significantly increase their defence spending. "I've been asking them to go up to 5 per cent for a number of years," Trump said Wednesday during his meeting with Mark Rutte, the alliance's secretary-general. "I think that's going to be very big news."