German President Horst Koehler resigned suddenly Monday over what he said was heavy criticism about comments he made on Germany's military role in the world, which he said had been misinterpreted.

It was the first time in German history that a president has resigned, the government-funded Deutsche Welle news agency reported.

Koehler said May 22 upon his return from a trip to Afghanistan that "in emergencies, military intervention is necessary to uphold our interests, like for example free trade routes, for example to prevent regional instabilities which could have a negative impact on our chances in terms of trade, jobs and income."

He later said he meant the protection of shipping routes along the Gulf of Aden against piracy, for example, and not any reference to Germany's role in Afghanistan. But his comments came in for widespread criticism.

Crticis said he was framing Germany's involvement in the Afghan war in economic terms having to do with self-interest, rather than as a duty in fulfilling a NATO mission in the fight against terrorism. Others said his comments indicated he would use the military unconstitutionally and for economic reasons.

Germany has 4,500 troops in a NATO-led force fighting a Taliban-led insurgency in Afghanistan.

Polls show that most Germans oppose the war in Afghanistan, but the government has not set a date for the withdrawal of troops.