US Secretary of State, Mike Pompeo, visited Cyprus on Saturday, calling for Turkey to desist from any activities that could further raise tensions in the Eastern Mediterranean.
Disputes between Ankara, Greece and Cyprus are centred around hydrocarbon resources and maritime influence in the region that have led to fears of conflict.
Turkey, which is hunting for gas and oil reserves in waters claimed by fellow NATO member Greece, last month deployed an exploration vessel backed by military frigates.
"We remain deeply concerned by Turkey's ongoing operations surveying for natural resources in areas over which Greece and Cyprus assert jurisdiction over the Eastern Mediterranean," Pompeo told reporters in Nicosia after a meeting with Cypriot President Nicos Anastasiades and Foreign Minister Nicos Christodoulides.
Greece increases military spending
The US is calling on all sides to back diplomacy, but as tensions rise, the Greek Prime Minister Kyriakos Mitsotakis has announced plans to boost his country's defence forces, including the purchase of 18 French fighter jets, four frigates and four navy helicopters.
"Τhe time has come to strengthen the armed forces as a legacy for the security of the country," Mitsokakis told a conference in Thessalonika.
France has sent warships to the Eastern Mediterranean in a show of support for Greece.
Turkish President Recep Tayyip Erdogan on Saturday stepped up his verbal attacks on France with a stark warning to the French president.
"France is often on the agenda. I don't want to give names, but I am forced to because he comes at me a lot. It isn't with our people, but he says: 'We have a problem with Erdogan.' Mr Macron, you are going to have way more problems with me," he said.
However, in a move that might be seen as more conciliatory Turkey confirmed on Sunday that a research vessel sent to the disputed zone in August has returned to the Turkish coast.
The EU has threatened Turkey with sanctions unless it ceases unilateral actions in the disputed area.