Germany's defence minister has said the US decision to withdraw 5,000 troops from his country was "foreseeable", as the Nato military alliance says it is seeking clarification from Washington.
Speaking to the DPA news agency, Boris Pistorius also stressed "the presence of American soldiers in Europe, and particularly in Germany, is in our interest and in the interest of the US".
Meanwhile Nato spokeswoman Allison Hart said the alliance was "working with the US to understand the details of their decision".
When asked on Saturday night about the withdrawal of troops, Trump said: "We're going to cut way down, and we're cutting a lot further than 5,000." He did not provide more details.
Washington's move comes after President Donald Trump criticised German Chancellor Friedrich Merz for saying the US had been "humiliated" by Iranian negotiators in the ongoing war.
Pentagon spokesperson Sean Parnell on Friday said the move followed a thorough review and recognised "theater requirements and conditions on the ground".
The US military deployment in Germany - currently at more than 36,000 active duty troops - is by far its biggest in Europe, compared with about 12,000 in Italy and 10,000 in the UK.
Trump has also suggested pulling US troops from Italy and Spain.
Last year, Washington decided to reduce its troop presence in Romania, as part of Trump's plan to shift the focus of US military commitment from Europe to the Indo-Pacific region.
There are now growing concerns within the 32-member Nato alliance that the US latest decision could weaken the organisation.
"The greatest threat to the transatlantic community are not its external enemies, but the ongoing disintegration of our alliance," Polish Prime Minister Donald Tusk warned on Saturday.
"We must all do what it takes to reverse this disastrous trend," he added.
And two senior US lawmakers from Trump's Republican party said that they were "very concerned by the decision to withdraw a US brigade from Germany".
"Rather than withdrawing forces from the continent altogether, it is in the US interest to maintain a strong deterrent in Europe," said Senator Roger Wicker and Representative Mike Rogers, who chair the Senate and House armed services committees respectively.
In Saturday's interview with DPA, Pistorius also said Europe must take greater responsibility for its security, and that Berlin would now be working more closely with allies on the continent.
"Germany is on the right track," he said, pointing out that his country has significantly boosted its military spending in recent years.
Trump had previously accused Germany of being "delinquent" because its military spending was well below Nato's target of 2% of economic output (GDP).
But that began to change under the previous government of Olaf Scholz and has continued under Merz's current government, with Germany now projected to spend €105.8bn (£91bn) on defence in 2027.
Overall, Germany's defence expenditure is set to reach 3.1% of GDP, taking into account other defence funds, including Berlin's continuing aid to Ukraine as its continues to fight against invading Russian troops.
In her post on X on Saturday, Nato's Allison Hart said the US decision to pull troops out of Germany "underscores the need for Europe to continue to invest more in defence and take on a greater share of the responsibility for our shared security.
"We're already seeing progress since allies agreed to invest 5% of GDP at the Nato summit in The Hague last year."
The latest spat between Trump and Merz was triggered by comments by the German chancellor on Monday.
Merz told students that "the Americans clearly have no strategy".
"The Iranians are obviously very skilled at negotiating, or rather, very skilful at not negotiating, letting the Americans travel to Islamabad and then leave again without any result," he said.
He added that the "entire nation" was being "humiliated" by Iran.
In response, Trump took to his platform Truth Social, saying Merz thought it was "OK for Iran to have a Nuclear Weapon" and "doesn't know what he's talking about".
This was soon followed by the US troop withdrawal announcement.
Parnell said the order had come from Defence Secretary Pete Hegseth.
"We expect the withdrawal to be completed over the next six to twelve months," the spokesman added.
Trump, a longtime critic of the Nato alliance, has been lashing out at allies over their refusal to participate in operations to reopen the Strait of Hormuz, a key oil shipping route.
Iran has severely limited traffic through the waterway, responding to US and Israeli strikes that began on 28 February.
The US has also enforced a naval blockade on Iranian ports in the Gulf.
