Peace negotiations between the government and the Taliban “will not be concluded before the end of March,” when Germany's annual mandate is due to expire, he told the Funke media group.
“That is why we must prepare for different scenarios, including a new mandate with the Bundestag”, Germany's lower house of parliament.
An agreement between the United States and the Taliban stipulates that all US forces should withdraw by May 2021.
But a top US official warned on Friday that President Joe Biden faced “serious dilemmas” as the deadline approaches, and the Taliban show no sign of ending their violence.
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The new US leader has ordered a review of the deal Washington cut with the Taliban last year. It promised the withdrawal of all foreign forces by May 1 in return for security guarantees from the militants and a commitment to peace talks with the Afghan government.
NATO defence ministers are also to discuss later this month whether the alliance's 10,000-strong mission should stay or go.
Donald Trump in his final days as US president unilaterally reduced US forces in Afghanistan to just 2,500 — the lowest since the start of the war in 2001.
Several groups in Germany's parliament, in particular the liberals and far-left, have called recently for a strategy of disengagement from Afghanistan after 20 years of military presence in the country.