A new US drawdown of roughly 5,000 troops from Germany over the next year prompted strong questions from both Nato allies and Republicans in Congress.

A Nato spokesperson said the defence alliance is looking for details on the US effort, which was announced on Friday, adding that Washington’s move underscores the need for Europe to continue to invest more in its own defence.

The alliance remains confident of its ability to provide for deterrence and defence as a shift towards a stronger Europe in a stronger Nato continues, the spokesperson said. Polish Prime Minister Donald Tusk said on Saturday the transatlantic alliance risks disintegrating and called on all members to reverse “this disastrous trend”.

President Donald Trump has been growing increasingly frustrated with European nations, accusing them of ignoring his requests for help in the US war with Iran. Trump has been threatening to reduce the US military presence in Europe, and also announced on Friday that he is increasing tariffs on cars and trucks from the EU to 25 per cent, which will have a disproportionate effect on German carmakers.

Roger Wicker, the Mississippi Republican who chairs the Senate Armed Services Committee, and House Armed Services chief Mike Rogers, a Republican from Alabama, expressed concern about pulling out thousands of troops in a joint statement on Saturday – a notable rebuke from the president’s own party.

“Prematurely reducing America’s forward presence in Europe before those capabilities are fully realised risks undermining deterrence and sending the wrong signal to Vladimir Putin,” the lawmakers said, referring to the Russian president.