Chancellor Friedrich Merz has risked further wrath of US president Donald Trump by insisting Germany will contribute to security in the Middle East only after the end of the US and Israel’s war with Iran.

Meeting the interim Syrian leader Ahmed al-Sharaa in Berlin, Merz warned that an extended war “could [impose a] burden last seen in the Covid pandemic or at the start of the Ukraine war”.

“If the necessary conditions are met, then Germany will of course be prepared to make its contribution to free ship traffic in the Strait of Hormuz,” he said.

Trump hit out at Merz and his cabinet members as “cowards” after the German leader described US strategy in the region as “a massive, open-ended escalation”.

“I have great doubts that there is a strategy,” said Merz on Friday. His minister for defence Boris Pistorius went a step further, saying: “This is not our war.”

Those remarks prompted firm pushback from Trump, who wrote on his social media platform: “When I heard the head of Germany say, ‘this is not our war’ about Iran, I said: ‘Well, Ukraine’s not our war, we helped, but Ukraine’s not our war’.”

Their falling out came nearly a month after a relatively harmonious Merz visit to the Oval Office and the rapid plunge in temperature prompted leading German commentator Robin Alexander to joke: “Merz is now, as they say in Trump circles, on the s**t list.”

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On Monday, leading Trump allies came out to back the president and attack the chancellor. Former US ambassador to Germany Richard Grenell said it was “weak or hypocritical” for Merz to “sit in the Oval Office beside president Trump and say one thing about Iran and, back in Berlin, says something completely different”.

“Iran could fire a ballistic rocket that could reach Berlin [yet] the German government doesn’t accept the risk from Iran,” said Grenell to Die Welt daily. “Anyone who didn’t take seriously the risk from Russia, like the [German] government did, and instead filled Russia’s war chest, should have learned a lesson.”

While Merz and Atlanticist allies have cooled on the Trump administration since the Iran war, some in the far-right Alternative for Germany (AfD) have gone one step further, demanding a total shake-up in bilateral relations.

“Let’s start that with the withdrawal of US troops from Germany,” said Thilo Chrupalla, an eastern German AfD co-leader.

Trump has repeatedly threatened to withdraw some or all of the 38,000 US soldiers still stationed in Germany, a Nato holdover from the Cold War era and the German unification treaty.

The Chrupalla proposal is likely to play well ahead of a September election in the eastern German state of Saxony-Anhalt, where US-critical views are widespread and the AfD is polling 38 per cent.