Trump’s criticism came after the German chancellor on Monday said the U.S. had been “humiliated by the Iranian leadership.”
“The Iranians are clearly stronger than expected and the Americans clearly have no truly convincing strategy in the negotiations either,” Merz said.
His office did not immediately respond to a request for comment from POLITICO.
Trump has slammed European allies for their reluctance to aid the U.S. in the conflict, especially after Iran effectively shut down the Strait of Hormuz, a critical channel through which roughly 20 percent of the world’s oil passes.
Europe spent the early days of the war resisting Trump’s call to take an active role.
“Europe has no interest in an open-ended war,” Kaja Kallas, the vice president of the European Commission, said in March. “This is not Europe’s war, but Europe’s interests are directly at stake.”
A German official, given anonymity to discuss sensitive conversations, questioned the virtue of Merz going after Trump on Monday.
“We can see that there is no one in Trump’s inner circle with diplomatic competence or foresight, and that his “art of the deal” is reaching its limits. We saw this already during the Ukraine negotiations. Nevertheless, it is not a wise statement by Merz, as it will drive a deeper wedge into transatlantic relations. Part of diplomacy is not speaking every truth out loud. Sometimes silence also has value.”
But Merz has been critical of the president’s leadership before.
In February, he told an audience at the Munich Security Conference that the U.S. could no longer be counted on to watch over the global world order. Trump’s leadership had spurred “a deep divide” between Europe and the United States, he said.
“The leadership claim of the U.S. is being challenged, perhaps already lost,” Merz said at the conference. “In the era of great powers, our freedom is no longer simply guaranteed. It is under threat.”
Jack Detsch contributed to this article.