Turkey's two key Western allies, the United States and Germany, on Tuesday urged it to pull back a ship it has returned to waters contested with Greece, with Washington denouncing the "calculated provocation."
The Turkish navy said Sunday that the Oruc Reis exploration vessel was heading back to energy-rich eastern Mediterranean waters between the Greek island of Crete and Cyprus, weeks after it left amid an agreement for talks.
In a strongly worded statement, the State Department said the US "deplores" the decision by Turkey and noted that Greece "asserts jurisdiction" over areas where the ship plans to operate through October 22.
"We urge Turkey to end this calculated provocation and immediately begin exploratory talks with Greece," State Department spokeswoman Morgan Ortagus said.
"Turkey's announcement unilaterally raises tensions in the region and deliberately complicates the resumption of crucial exploratory talks between our NATO allies Greece and Turkey," she said.
"Coercion, threats, intimidation and military activity will not resolve tensions in the Eastern Mediterranean."
Turkey last sent the ship into contested waters in August backed by warships, alarming both Greece and Cyprus, which is partially occupied by Ankara.
Greece responded by staging military exercises but tensions eased when both Ankara and Athens agreed to talk through the crisis.
- Greece to protest -
Greece said Tuesday there could be no diplomatic solution until the ship is withdrawn.
Greece "will not sit at the table for exploratory talks while the Oruc Reis and escorting warships are out there," Minister of State George Gerapetritis told Parapolitika radio.
He said Athens would "emphatically" raise the dispute at a European council meeting starting Thursday.
Turkey hit back at the US statement, noting that Washington does not recognize the so-called Seville Map by Spanish scholars that is cited by Greece for its maritime claims.
"It is thus a serious contradiction for the US to criticize Oruc Reis' seismic survey activities as carried out within the Turkish continental shelf," a foreign ministry statement said.
Turkish President Recep Tayyip Erdogan last month said the withdrawal of the ship was a chance to give diplomacy a chance.
But Turkish officials also insisted the ship was only undergoing planned maintenance.
- Germany steps up tone -
German Foreign Minister Heiko Maas, visiting Cyprus before heading to Greece, said that Turkey "must end the cycle of detente and provocation."
"It is now up to Turkey to create those conditions and the climate so that there is the possibility of conducting exploratory talks without further challenges," Maas told reporters in Nicosia.
"And the moment that this vessel embarks on a new search for hydrocarbons in the disputed maritime areas, this will truly be a serious blow to de-escalation efforts," he said.
While France has staunchly backed Greece throughout the standoff with Turkey, Germany had irked many Greeks in August with what they perceived as a low-key response by Europe's largest economic power.
Erdogan has a cordial relationship with German Chancellor Angela Merkel, who has worked with Turkey both on stemming the flow of Syrian and other refugees into Europe and over the crisis in Libya.
Cyprus has pressed for tough action on Turkey, until recently exerting leverage on the European Union by holding up unrelated sanctions on Belarus over its crackdown on pro-democracy protests.
Meeting Maas, Cypriot Foreign Minister Nikos Christodoulides said: "What we are most interested in is not the adoption of sanctions. It is how illegal actions are dealt with which no one in the EU disputes under any circumstances."
Erdogan has also cultivated close ties with US President Donald Trump, although Washington's relationship has been growing with Greece, in part thanks to Athens' warming ties with US ally Israel.
Under Erdogan, Turkey has been newly assertive on multiple fronts and has encouraged Azerbaijan's campaign to wrest control of the Nagorno-Karabakh area from Armenia.