Turkish Defense Minister Fikri Işık announced Monday that the two countries were discussing a deal to buy some of Russia’s most advanced weapons. The move comes nearly a year after Turkish forces exacerbated military tensions by shooting down a Russian fighter jet flying over the Turkey-Syria border.

Turkey wants to buy Russia’s S-400 “Triumph” anti-aircraft missile systems, which have been used by coalition forces in Syria. The sale of the weapons, known by NATO and western countries as the SA-21 Growler, is far from assured and could face multiple technical delays in the future, according to the Moscow Times.

Among those obstacles are the soured ties between the countries following the downing of that jet last year, potential pushback from Turkey’s NATO allies because the S-400 systems aren’t compatible with their missile systems and Moscow's concerns that selling the missiles to Turkey could pose a significant national security risk to Russia.

The negotiations were disclosed just a day after Turkey’s President Tayyip Erdogan was quoted saying that his country may abandon its effort to join the European Union and instead align itself with a security bloc dominated by Russia, China and Central Asian countries. Turkey and the EU have been in negotiations for 11 years and prospects for admission into the European economic alliance appear to slim. EU leaders have been highly critical of Turkey and its record on democratic freedoms, according to NBC News.

“Turkey must feel at ease. It mustn't say 'for me it's the European Union at all costs'. That's my view," Erdogan told reporters on his plane Sunday while flying back from a visit to Pakistan and Uzbekistan.

S-400 Triumph missiles have been used by Russia since 2007 when they were first deployed into combat. They have been set up primarily to defend Russian airspace near Moscow and in the Baltics.