U.K. Ambassador Kim Darroch’s resignation Wednesday will be a further deterioration of the relationship between the United States and the United Kingdom under Donald Trump’s leadership, according to a senior Democrat on the Senate Foreign Relations Committee.

Darroch’s resignation followed a number of tirades against him by Trump after several diplomatic cables were made public in which Darroch provided an unvarnished–and unflattering–view of Trump for his superiors back in London.

“I know Sir Kim Darroch well. He has served the United Kingdom extremely well as their ambassador here in our nation’s capital. And every country sends ambassadors overseas in part so that they can send back open, clear eyed, blunt assessments of how that other country views them and how it’s functioning. And the leak of this confidential cable has produced an unfortunate flap that has now led to the resignation of a very skilled career foreign servant,” said Sen. Chris Coons of Delaware. “I will point out part of what drove this was President Trump taking to Twitter to insult the ambassador, to insult Theresa May, the outgoing prime minister of the United Kingdom. We have long enjoyed a close and special relationship with the U.K. that is rooted in our shared values as well as our interests and I think it’s unfortunate that this latest flap has further accelerated some of the distance between us.

“They will choose a new prime minister in just a few weeks. And in any event there almost certainly would have been a new ambassador posted at that point,” Coons added. “So I think Sir Kim has done, you know, what was the right thing from a career perspective. I will be sad to see him go.”