France's President Emmanuel Macron gestures during the meeting with U.S. President Donald Trump, ahead of the NATO summit in Watford, in London, Britain, December 3, 2019. Ludovic Marin/Pool via REUTERS

WATFORD, England (Reuters) - French President Emmanuel Macron on Tuesday said he stood by his comments that NATO was experiencing “brain death”, and that the transatlantic security alliance needed to be clear what its core purpose was.

Speaking alongside U.S. President Donald Trump on the sidelines of a NATO summit, Macron said the alliance could not even agree on the modern-day definition of terrorism.