"The behavior and remarks by German politicians, who are acting as the sole voice of the EU institutions and NATO, are not just unacceptable, it is blackmail," Kammenos said in a statement obtained by RIA Novosti.
In his comment, Kammenos accused Germany of "undermining" European institutions. "That is, if Germany is not trying to abolish the European Union and NATO altogether," he added.
Greece's new ruling party Syriza and its Prime Minister Alexis Tsipras have recently criticized the European Union for its harsh sanctions toward Moscow.
This followed a statement by German Chancellor Angela Merkel last Saturday that ECB, European Commission and International Monetary Fund were unlikely to renegotiate Greece's outstanding debt in light of the billions already written off.