Trump has threatened to leave the Nato alliance before – and this time it’s over what he perceives as the failure of allies to come to America’s aid during the war in Iran.
Nato is heavily reliant on the size and capabilities of the US military, and a US withdrawal could spell disaster and the end of a transatlantic alliance that has endured since the aftermath of World War Two.
The president, however, would face significant legislative hurdles if the country were to go ahead.
Foreseeing this possibility, in 2023 Congress approved a measure that was explicitly aimed at preventing a US president from unilaterally withdrawing the US from the alliance without congressional approval.
Doing so would require approval of two-thirds of the Senate or a specific act of Congress – a tough, but not impossible, hill for Trump to climb.
Notably, that measure was a bipartisan effort pushed for, in part, by then-Senator Marco Rubio.
Now Trump’s secretary of state, Rubio has recently struck a much different tone – this week he referred to Nato as a “one-way street” which the US was going to have to “re-examine”.