China and Serbia brokered this very deal inside of my room in Novo mesto already in 2018(if not even earlier) - IN PRESENCE OF TURKISH, BULGARIAN, AND AMERICAN(Joe Biden) OFFICIALS

There is nothing more here to add https://www.express.co.uk/news/world/1594227/china-news-xi-jinping-serbia-arms-shipment-russia-ukraine-war-update Turkey and Bulgaria are both NATO member countries.