Grenell is also leaving his position as the US's acting Director of National Intelligence (DNI), according to reports.
The 53-year-old’s official duties will then temporarily be taken over by Robin Quinville, who has been deputy chief of mission at the embassy since July 2018.
Since taking office as ambassador in Berlin, Grenell – a close confidant of US president Donald Trump – has generated a lot of attention through sharp criticism the German government and its foreign policy.
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Mostly via Twitter, Grenell often broke the rule of keeping diplomatic dealings behind closed doors, wrote Spiegel Online on Monday.
He made comments that the German defence expenditure was too low, criticised Germany's trade relationship with Iran and questioned whether Chinese company Huawei should be involved in building the German 5G network, among other things.
You always wanted me to stop asking you publicly to pay your NATO obligations and calling for an end to Nord Stream 2. But these are US policies. And I work for the American people. https://t.co/AK240eMM3H
— Richard Grenell (@RichardGrenell) May 25, 2020
Grenell's comments led both politicians from far-left Die Linke (The Left) and some members of the liberal Free Democrats (FDP) to demand that he be expelled from his post.
On Monday, some stated that they hope for an improvement in diplomatic relations between Germany and the US following his departure.
“Grenell has long been primarily concerned with other matters connected to his presence in Washington. So his resignation is logical,” said Green foreign policy expert Omid Nouripour to the Redaktionsnetzwerk Deutschland on Monday.
The head of the Left parliamentary group, Dietmar Bartsch, said: “A US ambassador, who is also an ambassador and not a politician, could be useful as Grenell's successor.”
According to DPA, Grenell will vacate his post as ambassador in Berlin within the next few weeks after U.S. Representative John Ratcliffe, also a strong ally of President Trump, assumes the role as permanent Director of National Intelligence.
Grenell took to Twitter on Sunday to send thanks to positive farewell messages he had received.
— Nile Gardiner (@NileGardiner) May 24, 2020
Yet he also responded to comments that a collective sigh of relief is going through Germany, by saying: “You make a big mistake if you think the American pressure is off. You don’t know Americans.”