Trump's second broadside of the week against Merz came a day after he said he was considering the redeployment of some of the tens of thousands of US troops stationed in key NATO ally Germany.

"The Chancellor of Germany should spend more time on ending the war with Russia/Ukraine (Where he has been totally ineffective!), and fixing his broken Country, especially Immigration and Energy," Trump said on his Truth Social network.

He added that Merz should spend "less time on interfering with those that are getting rid of the Iran Nuclear threat, thereby making the World, including Germany, a safer place!"

Trump was apparently infuriated by Merz's comments on Monday that Tehran was "humiliating" the United States in negotiations to end the US-Israeli war on Iran that has just entered its third month.

The US leader's comments also come a day after he had a call with Russian President Vladimir Putin that Trump said focused mostly on ending the war in Ukraine, which Moscow's forces invaded in February 2022.

Trump has long said he could bring a quick end to the war there but has made little progress.