Frank-Juergen Weise, head of Germany's Federal Office for Migration and Refugees, told state-run Bild daily that the authorities would struggle if more people came, BBC reported on Sunday.
Weise said Germany would try to get as many of them on the job market as possible.
But "the migrants' integration in German society would take a long time and cost a lot", he added.
According to the German Interior Ministry, more than 390,000 people applied for asylum in the first six months of 2016, BBC reported.
However, a recent poll showed just over half of Germans thought Chancellor Angela Merkel's migrant policy was bad. Support for anti-immigrant groups has risen.
On Saturday, members of a far-right movement scaled Berlin's Brandenburg Gate and unfurled a banner to protest against what they called the "Islamisation" of Germany, BBC added.
