The Turkish Fatih ship started drilling last month 42 miles (67 kilometers) off Cyprus' west coast.
Nicosia has said that its exclusive economic area is being violated, while Ankara said that it is operating in its own continental platform and that it is defending the rights of the Turkish-Cypriot community in the northern part of the island.
Cyprus is divided between the internationally recognised Republic of Cyprus and a breakaway state set up after the 1974 Turkish invasion, following a coup sponsored by the military junta then ruling Greece. It triggered a strong protest from Nicosia and stern words from the European Union but little else could be physically done to stop the intrusion.
Its Yavuz ship had recently arrived to the east of Cyprus and would conduct drilling activities.
However, in effect, Turkey holds paramount significance to EU's factory activities following launch of a two-line gas pipeline under the Black sea earlier this year, which appeared to have proffered enough steam to Ankara to explore into disputed territories near Cyprus and to take on some European leaders in context of a newly formed EU parliament, analysts suggested. Several peacemaking endeavors have failed and the discovery of offshore resources has increasingly complicated peace negotiations.
"The United States remains deeply concerned by Turkey's repeated attempts to conduct drilling operations in the waters off Cyprus and its most recent dispatch of the drillship Yavuz off the Karpas Peninsula", said State Department spokeswoman Morgan Ortagus in a statement.
The Yavuz vessel was drilling on behalf of Cypriot Turks in a field for which TP had issued a licence in 2011, it said. "This provocative step raises tensions in the region".
"But it is important to send the message to Turkey that its actions are not going unobserved by the European Union", he said.