President Horst Koehler of Germany is resigning immediately, following criticism of remarks he made about German military deployments abroad.
Mr Koehler, whose job is largely ceremonial, had linked missions such as the Afghanistan deployment with the defence of economic interests.
The remarks, made in a radio interview after a brief visit to Afghanistan earlier in May, drew criticism from a number of German politicians.
He said that for an export-oriented country like Germany it was sometimes necessary to deploy troops "to protect our interests... for example, free trade routes".
Mr Koehler, 67, was re-elected last year to serve a second five-year term as president.
Announcing his resignation on Monday, he said it had been an honour to serve Germany as president.
With his wife standing next to him, Mr Koehler said he regretted that his comments could lead to a misunderstanding about a difficult question for the nation.
The BBC reports the Speaker of parliament's upper house (Bundesrat), Jens Boehrnsen, will be interim president.