Turkey's President Recep Tayyip Erdogan, right, points toward the city center as he speaks with NATO Secretary General Jens Stoltenberg during a meeting of NATO's Mediterranean Dialogue, in Ankara, Turkey, Monday, May 6, 2019.
Turkey's President Recep Tayyip Erdogan, right, points toward the city center as he speaks with NATO Secretary General Jens Stoltenberg during a meeting of NATO's Mediterranean Dialogue, in Ankara, Turkey, Monday, May 6, 2019.

ISTANBUL - NATO Secretary-General Jens Stoltenberg is visiting the Turkish capital amid escalating tensions between alliance members Turkey and the United States over Ankara's procuring of a Russian S-400 missile system.

The NATO chief’s visit is seen as a last-ditch attempt to persuade Ankara out of its purchase of the Russian missiles. 

Stoltenberg met with Turkish President Recep Tayyip Erdogan, along with Turkish Foreign Minister Mevlut Cavusolgu.

We "made evaluations on a wide range of issues, including NATO-EU relations and Turkey's S-400 purchase," Cavusolgu tweeted. 

Stoltenberg's visit comes only a matter of weeks before Moscow delivers its S-400 missile system to Turkey. Washington is warning of sanctions under the Countering America's Adversaries Through Sanctions Act, which bans significant weapon purchases from Russia.

U.S. officials claim the Russian missiles will compromise NATO defense systems, particularly the latest U.S. warplane the F 35, which Turkey is a joint production partner. The U.S. Pentagon warns the F-35 collaboration, along with the delivery of the jets, is also in jeopardy if the S-400s are delivered.

With time running out for a solution to the impasse, Erdogan emphasized what was at stake for NATO.

"We are at a time when threats such as terrorism are directly concerning the security of alliance," Erdogan said Monday in a speech, with Stoltenberg in attendance. "There are serious divergences in the international security atmosphere."

Analysts claim Stoltenberg was widely seen by Ankara as an honest broker in the S-400 controversy, avoiding taking sides and stressing the importance of dialogue. But he is hardening his stance.

"Decisions about military procurement are for nations to make," he said. "But as I have said, interoperability of our armed forces is fundamental to NATO for the conduct of our operations and missions," Stoltenberg said in an interview Sunday with Anatolia Agency, Turkey's state-run news organization.

“I welcome and encourage the discussions about Turkey’s possible acquisition of a U.S. Patriot missile system,” Stoltenberg said.

Washington is offering its Patriot missile system as an alternative to Russia's S-400.

Turkey's President Recep Tayyip Erdogan, center, a
Turkey's President Recep Tayyip Erdogan, center, and Foreign Minister Mevlut Cavusoglu, left, speak with NATO Secretary General Jens Stoltenberg during a NATO's Mediterranean Dialogue, in Ankara, Turkey, Monday, May 6, 2019.

?Until now, Ankara routinely claimed that only Washington was voicing opposition to the S-400 purchase. Turkish officials argued the dispute was a bilateral affair, rather than with NATO.

"This would never have happened if there had not been a vast erosion of trust between the two NATO allies triggered by several ongoing disputes. So, the context is important," said Sinan Ulgen, head of the Istanbul-based think tank, Edam. 

Analysts claim Ankara's portrayal of the missile controversy as a bilateral affair runs the risk of a dangerous diplomatic miscalculation. 

"NATO Secretary-General Jens Stoltenberg tells Turkey that every ally has the right to choose any system, they have that right to buy," said international relations professor Huseyin Bagci of Ankara's Middle East Technical University. "But the political consequences of buying the strategic systems, he does not say anything."

Stoltenberg is walking a diplomatic tightrope, with NATO relying heavily on Turkish military support. 

"Turkey is a highly valued ally, and NATO stands in solidarity with Turkey as it faces serious security challenges," Stoltenberg tweeted Monday.

Turkey has the second-largest army in the alliance after the United States, with its forces participating in operations from the Balkans to Afghanistan. In 2020, Turkey will take command of the NATO Response Force.

With Turkey bordering Syria, and the main transit route for many jihadists seeking to return home to Europe, Ankara is seen as vital by most of its NATO European partners in counterterrorism and intelligence cooperation.

Analysts claim such cooperation explains why Washington remains mostly alone in its public opposition to Turkey's pricing the S-400 missile system.

However, Erdogan reminded Stoltenberg that Ankara, too, has its concerns over the commitment of its NATO partners. 

"We expect our friends in NATO to act only in accordance with the spirit of the alliance and to hold the alliance's founding values," Erdogan said, referring to Turkey's fight against terror groups. 

Ankara is frustrated over the support lent by Washington and other European countries to Syria's Kurdish militia, the YPG, in the war against Islamic State.

Until now, all sides appear ready to avoid any confrontation over the simmering tensions and disputes. But with the looming delivery of the S-400 to Turkey, analysts warn it could be a catalyst for a rupture in the alliance.