US Secretary of State Mike Pompeo paid a fraught visit to Istanbul on Tuesday that included no official meetings and an agenda focused on religious freedoms that Ankara dismissed as "irrelevant".

Ties between Washington and its strategic NATO ally have remained tense despite a personal friendship between US President Donald Trump and his Turkish counterpart Recep Tayyip Erdogan.

A group of 20 to 30 Turks shouted "Yankee go home!" as the evangelical Christian Pompeo headed in for a meeting with the Patriarch Bartholomew I of Constantinople -- the spiritual leader of the Greek Orthodox world -- to express his "strong position" on religious freedoms.

Pompeo had publicly criticised Erdogan's controversial conversion of Istanbul's emblematic Hagia Sophia monument into a mosque in July. 

"An incredible privilege to be here," Pompeo told the patriarch.

The foreign ministry declared ahead of Pompeo's arrival that the US should "first look in the mirror" before making an issue of the "completely irrelevant" subject of the freedom of faith in Turkey.

Preparing for Biden 

Pompeo's seven-nation tour has been complicated by his unabashed support of Trump's unsubstantiated claim of election fraud -- and attempts by US allies to position themselves for Joe Biden's incoming presidency.

The US diplomat's two-night stay in Paris included a meeting with French President Emmanuel Macron but no press conference that usually follows such talks.

Yet the Turkish leg seemed destined for problems from the start.

Officials said Pompeo wanted to visit Istanbul to see the patriarch and was only ready to meet Erdogan and Turkish Foreign Minister Mevlut Cavusoglu on the condition they come to him from the capital Ankara.

A meeting seemed possible after intense negotiations before the talks fell apart.

"This was a scheduling issue," a senior US official said.

"President Erdogan's schedule shifted and made it impossible to fit the parameters that from the very beginning we had set out".

It is difficult to gauge whether the election of Joe Biden -- whom Erdogan congratulated three days after his victory was called by US media -- played a role in the imbroglio.

But it will mean Pompeo will fail to discuss with Turkish officials the very problems he pointed to Monday after a meeting in Paris with Macron.

'Very real' sanction threat 

"President Macron and I spent a lot of time discussing Turkey's recent actions and we agreed they are very aggressive," Pompeo told the French daily Le Figaro.

Macron has sparred with Erdogan on a range of regional issues and shares Pompeo's mistrust of Turkey's robust foreign policy stance.

Pompeo cited Turkey's "support" to Azerbaijan in the Nagorno-Karabakh conflict with Armenia and repeated claims denied by Ankara that it had "deployed Syrian forces" in support of the Azerbaijani troops.

"We also mentioned its action in Libya where it also sent forces from third party countries, and its action in the eastern Mediterranean. I could continue this list," Pompeo said.

"Europe and the United States must work together to convince Erdogan such actions are not in the interest of his people."

The issues add to the dispute over Ankara's controversial acquisition of Russian advanced S-400 anti-missile systems.

The purchase, according to US law, should trigger immediate sanctions but Trump gave Turkey a reprieve.

The Turkish military tested the S-400s just weeks before the US vote.

"Sanctions is very much something that is on the table" and are a "very real" possibility, the US State Department warned last month.

The visit coincides with the publication of a New York Times report saying Trump last week asked his aides -- including Pompeo -- about the possibility of striking Iran's nuclear facilities.

The officials "dissuaded the president from moving ahead with a military strike," the report said.

Pompeo had no scheduled press conferences at which he could address the story.