"I do not see the date when we can stop it," de Maiziere told the public broadcaster MDR.
The main focus is said to be currently on the border with Austria, as the biggest number of refugees are arriving in Germany via this country. The temporary border controls have been extended several times, and are now set to be in place until February 13.
According to Article 23 of the Schengen Borders Code, in case of a serious threat to public policy or internal security, a member state may exceptionally reintroduce border controls on at its borders for a limited period of no more than 30 days. The temporary border controls can be extended for another 30 days, if the threat remains.
Germany has been the main destination for the hundreds of thousands of refugees coming to Europe from the Middle East and North Africa. According to the country's Interior Ministry, over 1.1 million refugees arrived in Germany in 2015.