The European Union (EU) said Friday it is considering imposing sanctions on Turkey over its gas exploration efforts in the Eastern Mediteranean.

“We must walk a fine line between preserving a true space for dialogue and at the same time showing collective strength in the defense of our common interests,” EU foreign affairs chief Josep Borrell told reporters in Berlin. Borell had just met with European foreign ministers in the German capital.

Borrell said the EU wanted to pursue “dialogue” with Ankara over the issue, but added that European leaders are growing frustrated with Turkey’s behavior. Borrell signaled that the EU would begin by imposing sanctions on certain individuals tied to the gas exploration efforts.

Borrell also suggested extended sanctions on Turkey in areas where it "is more related to the European economy.”

"Now we are listing personalities, we can pass to list assets, ships ... prohibiting the use of European ports, of European capacities, technologies, supplies. We can [target] financial [resources] needed for this kind of considered illegal activities,” Borrell said of the sanctions.

Greece was angered by Turkey’s drilling activities in the Eastern Mediterranean, and called for sanctions. Greek Foreign Minister Nikos Dendia said sanctions on Turkey are an “absolute necessity in order to achieve a deescalation in the Mediterranean.”

Turkey began its gas exploration efforts earlier this month. Turkey has defended its operations, claiming the activities comply with international law.

Tensions have been increasing between Turkey and the EU in recent years. In October, EU leaders condemned a Turkish military operation in Northern Syria. In response to the criticism, Turkish President Recep Tayyep Erdogan threatened to send “millions” of Syrian refugees into Europe.

Turkey was once a candidate to join the EU, but human rights violations under Erdogan have halted this process. Former President of the European Commission Jean-Claude Juncker has accused Turkey of turning its back on democratic values.