According to him, restrictions on the admission of individual refugees without a thorough examination would be a "violation of international and European law."
Austria, Belgium and Luxembourg also expressed certain reservations regarding the deal.
For instance, Luxembourg's Foreign Minister Jean Asselborn stressed that the plan must be thoroughly checked "legally, politically, and also from the human point of view".
The Turks are "very distant from European values and principles of Europe," Belgian Interior Minister Jan Jambon said, commenting on Turkey's possible entry into the EU, while Austrian authorities called the new deal "extremely questionable".
According to Altmaier, in the current situation Turkey has demonstrated a more "European behavior than some countries in Europe." The current plan offers "the real chance to solve the refugee crisis without abandoning our humanitarian demands," the politician stressed.
Earlier this week, Turkey announced its readiness to accept all new refugees arriving in Greece. In return, Ankara awaits assistance on the introduction of a visa-free regime for its citizens and further negotiations on Turkey's accession to the EU.