A German university on Thursday gave the country's defense minister two weeks to respond to allegations that he plagiarized part of his doctoral thesis.

Bayreuth University, which accepted his thesis in 2007, said it notified Karl-Theodor zu Guttenberg of the deadline in a letter, German news agency DAPD reported.

Guttenberg was out of the country Thursday on a previously unannounced visit to German troops in Afghanistan. Polls regularly rate him Germany's most popular politician, and the plagiarism flap has prompted opposition figures to cast doubt on his political future.

Guttenberg on Wednesday dismissed as "absurd" the allegations of plagiarism first reported by German daily Sueddeutsche Zeitung. However, the minister said in a written statement that he is willing to check whether there were any omissions or errors among the 1,200 footnotes in the 475-page thesis.

The 39-year-old Guttenberg has built a reputation as a plain-speaking man of action. As defense minister, he has pushed through a plan to end conscription.

Guttenberg could eventually lose his doctoral title if an investigation concluded that the alleged omissions amounted to fraud. The possible consequences for his political career are unclear, though his thesis supervisor has dismissed the accusation of plagiarism.

Guttenberg is "in danger of losing the necessary overview" as he defends himself, said Gernot Erler, a senior lawmaker with the main opposition Social Democrats. "A defense minister with tarnished authority won't be able to manage any tasks successfully."

"I hope it isn't true, but if it is, then I think his days as a minister are numbered," Gregor Gysi, the parliamentary leader of the Left Party, also in opposition, told ARD television.