Foreign relations

Such a solution would include the involvement of neighbouring Pakistan, Steinmeier said during his unexpected two-day visit to Kabul, which had been kept under wraps for security reasons.

As long as a regional solution including Pakistan is not in place, "our efforts in Afghanistan will only have limited success," Steinmeier said after his meeting with President Hamid Karzai.

Pakistan a refuge for militants

Pakistan's border region with Afghanistan serves as a refuge for militants who often launch attacks into Afghanistan.

The trip is Steinmeier's fourth to Afghanistan since taking office at the end of 2007.

Chancellor Angela Merkel visited German troops stationed in the north of the country three weeks ago but did not meet with Afghan leaders.

Germany has about 3,800 troops deployed to Afghanistan, and plans to increase that number to 4,400 in the coming months as Afghanistan prepares for presidential elections in August.

Criticism for Karzai

Incumbent Karzai, who has been in office since 2001, has faced rising criticism over the past months from his Western backers, who accuse him of not doing enough to stem corruption in the country.

In addition to meeting with Karzai, Steinmeier was set to hold meetings with Foreign Minister Rangin Dadfar, and Interior Minister Hanif Atmar. It was not immediately clear if Steinmeier would meet with German troops in Afghanistan.

Meanwhile, on the day he arrived, five German soldiers were wounded in a suicide attack in the northern Afghanistan province of Kunduz.