Germany is being hampered in its efforts to repatriate migrants from north Africa.
It has called on officials from Algeria and Morocco to expedite the acceptance of those of their nationals who have no residence permits for Germany so that it can better concentrate on dealing with asylum seekers seeking to dodge violence and war.
The process of returning people has been slow as the countries of their origin have been reluctant to accept them because of missing identity documents.
"We have a repatriation agreement. That means everything is regulated on paper. But in practice, we know that it remains problematic in some cases," said government spokesman Steffen Seibert.
"That must be dealt with so that the agreement can be put into action."
All foreigners without residency rights in Germany are required to leave, including citizens of North Africa, he said. "And there we have to talk about how the repatriations can be carried out."
The numbers of Algerian migrants arriving in Germany went from 847 in June to 2,296 in December, while those from Morocco jumped from 368 to 2,896, the interior ministry said.
Chancellor Merkel raised the issue this week during Algeria's Abdelmalek Sellal visit, but the Algerian premier said acceptance was conditional on "ensuring that they really are Algerians".
The same message was delivered by a Tunisian foreign office official.
"The state has to ensure that the migrants are really Tunisians. Sometimes these checks take time," he said.
The matter has been driven higher on the agenda after the sexual assaults on women during the New Year’s Eve celebrations, particularly in Cologne where 331 of the 652 complaints relate to sexual violence.
So far 19 suspects have been identified by Cologne police, of whom 14 are from either Morocco or Algeria.
