Pete Hegseth, the new US defence secretary, spoke with his British counterpart John Healey by phone on Friday in their first conversation since taking office, Sky News can reveal.
Two sources confirmed the exchange had taken place.
The content of the conversation has yet to be revealed.
London will be hoping to retain the special military relationship with Washington – a fundamental pillar of UK security. The US is also a vital member of the NATO alliance and a crucial partner in supporting Ukraine to combat Russia’s invasion.
Defence spending and the shrunken size of the UK armed forces could be a point of friction between Britain and the new US administration, however.
Donald Trump has said he believes his NATO allies should be spending at least 5% of national income on their militaries. Sir Keir Starmer’s government has yet to say by when it expects UK defence spending to inch up to 2.5% from around 2.3%.
