Europe is watching closely how the appointment of the hawkish John Bolton as US National Security Adviser could effect the relationship with some of America's closest allies. Bolton is skeptical of the traditional diplomacy common in the EU in favour of transactional deals and hard power.
He has already descibed any negotiations with North Korea as a 'waste of time', a sentiment Jacob Parakilas of the US and the Americas Programme at Chatham House believes could have devastating consequences.
" Frankly, I think we should be a bit worried," he says. "Bolton as with Iran has called for pre-emptive strikes against the North Korean nuclear programmes, the North Korean missile test facilities and so on. I think it's difficult to imagine a scenario where this doesn't escalate into a full-scale war."
Closer to home, Parakilas says Bolton's stance on Russia is much closer to the European position. He feels there should be a much stronger reaction to allegations of Russian interference in elections which puts him at odds with President Trump.
" How that relationship plays out," he says. "How Bolton and Trump's differing views on the nature of the Russian challenge to Western institutions and Western poiltical action is going to be, I think, a hugely important story within the White House and within the US adminstration and again with fairly unpredictable repercussions for the Transatlantic relationship and beyond."
Bolton has less power than the Defense Secretary and Secretary of State. But he works in the same building as the president. And Donald Trump has already shown how much he cares about opinions that are directly expressed to him.
This could give the new National Security Adviser a direct line to the President's ear.