America's top diplomat Mike Pompeo left Washington on Sunday for Greece, where he intends to call for the de-escalation of tensions in the eastern Mediterranean and encourage a nascent dialogue with Turkey.

The secretary of state's first stop on a mini European tour will be Thessaloniki, in northern Greece, on Monday, where he will meet his counterpart Nikos Dendias.

On Tuesday he will head for Crete to meet with Prime Minister Kyriakos Mitsotakis and visit the NATO naval base in Souda Bay. The tour also includes stops in Italy, the Vatican and Croatia.

Greece and fellow NATO member Turkey are at loggerheads over energy exploration in disputed waters after Ankara stepped up hydrocarbon research activities in the sea.

But on Tuesday they said they were ready to start talks over the tensions, which have been running high for weeks.

The US has been vocal on "the need to de-escalate in the Eastern Med," a senior US official told journalists before the tour, stressing that Pompeo had "expressed his deep concern."

He also wants to embrace "the recent positive developments and the prospect of return to dialogue," the official added.

The official insisted on the need to reduce "the likelihood of any accidents or incidents," and called for "Greece and Turkey to move forward on that and ideally be able to ... complete an agreement."

Washington encourages "all states to resolve maritime delimitation issues peacefully and in accordance with international law," he continued.

The visit to Thessaloniki is also intended as a sign to the Balkans on American willingness to invest in the region, the State Department said.

Pompeo will travel Wednesday and Thursday to Rome to meet with Italian authorities.

There he will discuss efforts by the Trump administration to deter its European allies from using equipment by Chinese manufacturer Huawei in developing their ultra-fast 5G cell-phone networks.

With Sino-American trade tensions rapidly turning into a new Cold War, the US president is accusing Huawei of being a tool for Beijing's espionage.

Pompeo is also scheduled to attend a meeting at the Vatican on religious freedom, his human rights priority. There, too, he will warn of China's actions against minorities, including Muslims.

Finally, he will make a brief stop in Dubrovnik, Croatia, on Friday.