Relations between the US and Germany are dogged by more "uncertainty" than at any time in their history, claims the German president.
Frank-Walter Steinmeier said there has "never been so much uncertainty in the history of the German-American relationship and in the transatlantic relationship as there is at the present moment".
The leader was speaking to German TV station ZDF during an interview on Sunday (23 July).
During his US presidential election campaign, Donald Trump frequently questioned the value of the European Union, welcomed Britain's vote to leave the bloc in June 2016 and spoke positively of anti-EU politicians such as the French far-right leader Marine Le Pen.
In Germany the president's role is largely ceremonial and the holder is generally expected to show restraint in discussing political opinions.
But Steinmeier – who became President in March – has been outspoken about his views on Trump in the past, saying that he would make foreign relations "more difficult" and blaming the American leader for divisions in the US.
The interview comes after chancellor Angel Merkel said it was "regrettable" that Trump refused to sign up to a communique at last month's G20 summit in Hamburg pledging to implement the Paris climate accord to cut greenhouse gas emissions – which he wants to scrap or totally re-work. The other 19 members of the G20 did recommit to the agreement.
Also, Merkel, regarded as Europe's most influential leader, said at an election rally in Munich in May that the continent could no longer rely on its longstanding British and US allies after Brexit and the election of Trump in November.
She said: "The times in which we could completely depend on others are, to a certain extent, over. We Europeans truly have to take our fate into our own hands."
In his TV interview Steinmeier admitted that German democracy "would not exist without the Americans", referring to the Allied forces' work to rebuild Europe after the Second World War.
"Our economic development would not have happened without the Marshall Plan," he said, referring to the US initiative to pump billions of dollars into Western Europe to revive their economies after the ravages of the Second World War.
Steinmeier added: "In this respect, I advise us not to throw everything overboard, even though I admit that I am irritated about a lot of things."