ISTANBUL  — U.S. Secretary of State Mike Pompeo met with the Istanbul-based spiritual leader of the world's Orthodox Christians on Tuesday during a short trip to Turkey that raised the ire of Turkish officials and included no meetings with any of them.

Pompeo, who is on a seven-country tour of Europe and the Middle East, tweeted pictures of him being greeted by Ecumenical Patriarch Bartholomew I, the leader of around 300 million Orthodox Christians, after being shown around the Patriarchate. He also met with the apostolic nuncio to Turkey, Archbishop Paul Russell. 

The talks were to center on religious freedoms in Turkey, which has angered Ankara and prompted officials to call on Washington to focus on human rights violations in the United States.

Last week, Turkey issued a sharply-worded statement criticizing Pompeo's plans and said Washington should "look at the mirror" and deal with issues such as racism, Islamophobia and hate crimes. 

But the talks went ahead, and Pompeo on Tuesday tweeted that "as leader of the Orthodox world" Bartholomew "is a key partner as we continue to champion religious freedom around the globe."

Wearing an American-flag face mask, Pompeo later toured the nearby Rustem Pasha Mosque, which was built by the Ottoman architect Sinan and is known for its elaborate blue-and-white tilework. His wife, Susan, wore a mask and also a headscarf during the tour in line with Muslim traditions.

The trip comes amid already frayed ties between the two NATO allies over a series of issues, even though Turkish President Recep Tayyip Erdogan and U.S. President Donald Trump have maintained friendly personal ties. 

Those include Turkey's decision to purchase Russia's S-400 anti-aircraft system, which Washington says is a threat to its F-35 fighter aircraft. Washington has kicked Turkey out of the F-35 program and has also threatened to sanction the country.

Senior officials at the U.S. State Department said the lack of official meetings in Turkey was due to scheduling issues during the brief stop. They said meetings had been sought, but Turkish officials were unable to come to Istanbul from the capital, Ankara, during the time Pompeo would be there. The officials noted that Pompeo and his Turkish counterpart plan to see each other in early December at a meeting of NATO foreign ministers.

Turkish media reports said Turkish officials were giving Pompeo the cold shoulder, after he allegedly refused to travel to the capital to pay an official visit. A senior Turkish Foreign Ministry official wouldn't comment on the reports or say why Pompeo wasn't meeting with Turkish officials. 

Turkey insists that it protects the rights of citizens of various faiths to freely practice their religions even though it recently drew criticism, including from Pompeo, for reconverting Istanbul's landmark Haghia Sophia into a mosque, ignoring calls for the former cathedral to be kept as a museum in recognition of the city's multicultural past.

Meanwhile, around 25 members of a left-wing nationalist group, the Turkish Youth Union, staged a brief demonstration near the Patriarchate under heavy police presence, protesting Pompeo for meeting with Bartholomew instead of state officials. The demonstrators chanted "Down with U.S. imperialism" and "Yankee go home."

Later stops on Pompeo's tour will include visits to Israeli settlements in the West Bank that have been avoided by previous secretaries of state.