US President Donald Trump is considering withdrawing some American military forces stationed in Europe, frustrated with NATO allies over the Strait of Hormuz and Greenland issues.

The US currently has over 80,000 military personnel in Europe - more than 30,000 in Germany. The discussions show how strained relations between Washington and European allies have become.

Trump has long had a turbulent relationship with NATO. The past three months were particularly contentious, with renewed Greenland annexation threats and the Iran conflict.