Foreign Minister Mevlüt Çavuşoğlu held a constructive phone call with his U.S. counterpart Anthony Blinken, ministry sources said Monday.

The two ministers discussed bilateral issues, the Afghanistan peace process and the planned meeting in Istanbul, as well as developments in Syria and the Middle East, sources said, calling it a “constructive and fruitful meeting.”

This was the first time Çavuşoğlu and Blinken spoke after their meeting on the sidelines of the latest NATO foreign ministers’ summit in Brussels last month.

“Turkey is a long-standing and valued ally,” Blinken had told an event at NATO headquarters, saying it was also in Ankara’s interest to remain in the alliance.

The two top diplomats had their first phone call under the new Joe Biden administration in February.

Ties between NATO allies Turkey and the U.S. were badly strained over Ankara’s acquisition of the advanced S-400 Russian air defense system, prompting Washington to remove Turkey from its F-35 Lightning II jet program.

The U.S. argued that the system could be used by Russia to covertly obtain classified details on the Lockheed Martin F-35 jets and is incompatible with NATO systems. Turkey, however, insists that the S-400 would not be integrated into NATO systems and would not pose a threat to the alliance.

Ankara has repeatedly stressed it was the U.S.' refusal to sell it Patriots that led it to seek other sellers, adding that Russia had offered a better deal, including technology transfers. Turkey even proposed setting up a commission to clarify any technical issues.

Issues, including Syria, the S-400 missiles and the extradition of Fetullah Gülen – the mastermind of the July 15 coup attempt orchestrated by the Gülenist Terror Group (FETÖ) – as well as U.S. support for the YPG/PKK terrorist organization threatening Turkey’s security, have led to mounting tensions between the two partners.

However, intra-Afghan peace talks emerge as an area of cooperation between the two countries. Earlier this month, Blinken proposed a United Nations-led peace conference in Turkey with the aim of finalizing a peace agreement in a letter to Afghanistan's President Ashraf Ghani. Following the news, Turkey expressed its readiness to take part in mediation efforts to establish peace in Afghanistan and the region.