Deportation is only possible when countries cooperate with German authorities, Interior Minister Thomas de Maizière warned | Sean Gallup/Getty Images Germany threatens aid cut to countries that refuse rejected migrants States that block deportations from Germany should be punished, politicians say.

German politicians have warned they may stop development aid to countries that won't take back migrants whose applications for asylum have been denied, der Spiegel reported Monday.

Authorities could not deport Anis Amri, the man suspected of orchestrating the Berlin Christmas market attack that killed 12 in December, because Tunisian authorities were slow to issue the necessary paperwork, according to der Spiegel's report.

Deportation is only possible when countries cooperate with German authorities, Interior Minister Thomas de Maizière told German broadcaster ARD on Sunday.

Over the weekend, protestors in Tunis demanded the government not allow radicalized Islamists to return to the country, die Welt reported. An estimated 5,000 Tunisians have joined Islamic State.

Tunisian Prime Minister Youssef Chahed deflected blame for the Amri case, saying the 24-year-old was known to Tunisian authorities only for minor delinquencies and became radicalized in Europe.