Donald Trump has promised to pull out "a lot" more than 5,000 soldiers from Germany following a spat with Chancellor Friedrich Merz.
Last week, Merz said the US was being "humiliated" in its war against Iran and criticised Washington's lack of strategy.
The initial announcement of the withdrawal of troops was made by the Pentagon on Friday. Around 36,000 US troops are stationed in Germany and withdrawal of 5,000 would result in the lost of around one seventh of military personnel.
The Pentagon has not elaborated on which troops or operations will be affected, merely stating that withdrawal of 5,000 soldiers will occur over the next six to 12 months.
At a press conference in Florida on Saturday, Trump declined to offer a reason for the move but vowed an even larger reduction was on its way.
He said: "We're going to cut way down. And we're cutting a lot further than 5,000."
Germany appeared to greet the news as "expected" following years of threats from Trump over military withdrawal.
Boris Pistorius said European nations must take a proactive stance on providing their own defence, while adding that security cooperation benefited both the US and Europe.
He said: "The presence of American soldiers in Europe, and especially in Germany, is in our interest and in the interest of the US."
Trump is said to be angered at European allies' refusal to join his war with Israel against Iran. Besides Merz, he has fired criticism at Spanish Prime Minister Pedro Sánchez and British Prime Minister Keir Starmer.
In a further sign of deteriorating relations, Trump alleged the European Union was not abiding by the terms of its US trade deal and announced further tariffs next week of 25 per cent on imported cars and trucks.
Such a move would be particularly harmful to Germany, which is a major vehicle manufacturer. It has led to further criticism of Trump from US politicians, with at least one branding the US president's conduct "unacceptable" and a breach of trade agreements.
Writing on X, Nato spokesperson Allison Hart said the trans-Atlantic alliance was “working with the US to understand the details of their decision on force posture in Germany” while pointing out “progress” on a target for Nato allies to invest 5 per cent of their economic output in defence
She added: “This adjustment underscores the need for Europe to continue to invest more in defense and take on a greater share of the responsibility for our shared security.”
