ANKARA, Turkey — Turkey and Ukraine's biggest defense firms have started negotiations that will most likely end up in a cooperation deal for tank modernization programs.

Turkish Aselsan and Ukraine's Ukroboronprom are exploring ways to undertake joint programs designed to upgrade tanks.

The cooperation will later expand into upgrading artillery and personnel carriers, one Aselsan official said.

The Turkish-Ukrainian talks came at a time when Russia, Turkey's top trade partner and main natural gas supplier, became both countries' foe.

Last year Russia annexed Ukraine's Crimea. Russian jets flying over Turkey's border with Syria began violating Turkish airspace in November , which led Turkish F-16 jets to shot shoot down a Russian SU-24 on Nov. 24, citing renewed violation.

The incident triggered the worst Turkish-Russian crisis in modern history. Russia has vowed to "make Turkey pay for this " and launched a slew of economic and commercial sanctions.

Russian President Vladimir Putin said the sanctions on Turkey will not be economic and commercial only.

Military electronics specialist Aselsan announced Nov. 30 that it signed a contract with the Turkish government to produce and deliver an indigenous system designed to protect tanks and armored vehicles from anti-tank rockets and missiles.

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Aselsan has been developing what it dubs the "Active Protection System," or AKKOR in its Turkish acronym, since 2008, and has been testing the system's radar, mission computer and ammunitions since 2010.

Aselsan said the AKKOR is designed to detect rockets and missiles targeting tanks and hit them while in the air.

The system is designed for the Altay, an indigenous next generation battle tank Turkey has been developing. But the firm said the AKKOR can also be outfitted to various types of armored vehicles.