JOIN USEuropean Council chief Charles Michel said Friday that Turkey has not de-escalated its stand-off with Greece and warned EU members now need to consider tougher options.
"I think that the cat and mouse game needs to end," Michel said, referring to Turkey's repeated incursions into Greek waters with gas exploration vessels.
"We will have a debate at the European summit on December 10 and we are ready to use the means at our disposal," he added.
Next week's EU summit will be held in Brussels with leaders meeting face-to-face after videoconferences were held as a coronavirus prevention measure.
One possibility, backed by some members, would be economic sanctions, but many states are not convinced.
EU foreign policy chief Josep Borrell told a conference in Italy "the EU Council will have to take the decision that only the EU can take, because the sanctions regime, it's a matter for the member states."
"There are not very many positive signals that came from Turkey during these months -- in Cyprus and on the drilling, the talks between Greece and Turkey have not been developing," he said.
Turkey has been challenging Greece over maritime territory in the Eastern Mediterranean, repeatedly sending a gas exploration vessel into Greek waters.
Both countries are NATO members and the alliance has set up a "de-confliction mechanism" to help avoid accidental military clashes.
But a German-led diplomatic approach to Ankara has made little progress in resolving the underlying issues, and some EU members -- notably France and Greece itself -- are pushing for stronger action.
Other EU capitals are more cautious, some fearing an escalating stand-off could see Turkish president Recep Tayyip Erdogan's government once again allow a wave of refugees to head for EU borders.
Michel, who will host the summit, expressed Europe's frustration.
"In October, after a very dense and strategic high level exchange, we defined a very positive offer to Turkey, we extended our hands," he told a news conference to mark his first year in office.
"But the condition to move in that area is that Turkey needs to stop unilateral provocations, hostile statements, and the non-respect of international principles and rules-based society.
"Well, since October, things have not been very positive," Michel noted.
"Since that time, we've seen that there have been unilateral acts that have taken place, a hostile rhetoric has been expressed."
Backed by Turkish navy frigates, the research vessel the Oruc Reis was first deployed in August and again in October to the waters off Kastellorizo island, in defiance of EU and US calls to stop.
It returned to port again in October, but may go back to the disputed zone while Ankara says that, with its long Mediterranean coastline, its claim to sovereign waters in the region is stronger than Greece's, which is based on its ownership of tiny Kastellorizo.