The S-400 acquisition is one of several issues that have frayed ties between the two allies, and has anxious some in the West that Turkey is drifting closer to Moscow's sphere of influence.
"We are aware of Turkey taking delivery of the S-400".
At the time, Trump acknowledged the US had a "complicated" situation, when it came to responding to Turkey, and noted that possible sanctions were being discussed. Turkey has had a nuclear role in North Atlantic Treaty Organisation for decades, but this new split is likely to cause some in Washington to question the wisdom of keeping those nuclear bombs at Incirlik.
Turkey has refused to bow to USA pressure, insisting that choosing which defense equipment to purchase is a matter of national sovereignty.
Russia's Federal Service for Military-Technical Cooperation confirmed on Friday it had started delivering the S-400 systems and that the deliveries would continue in accordance with an agreed schedule, the RIA news agency reported. "This is not only a problem between Turkey and the United States, but it is a problem between Turkey and the rest of the 28 North Atlantic Treaty Organisation members, so it's a serious problem".
Ankara and Washington are also involved in disputes over strategy in Syria east of the Euphrates River, where the United States is allied with Kurdish forces that Turkey views as foes.
A Turkish Defense Ministry video showed two planes landing at the air base and unloading various military trucks, some of which appeared to be carrying parts of the system.
Turkish media reports have said Turkey is expected to take delivery of two S-400 batteries.
The Obama White House "wouldn't let him buy the missile he wanted to buy, which was the Patriot", Trump told reporters during the G20 summit in Osaka, Japan last month. USA military and intelligence officials have warned for months that allowing the Russian system to operate within the same network as the F-35 would provide Moscow with sensitive information on how to defeat the technologically sophisticated fighter jet that is slated to become a critical element of many North Atlantic Treaty Organisation and partner countries' air forces.
Turkey says the system is a strategic defence requirement, particularly to secure its southern borders with Syria and Iraq.
Turkey's dollar bonds dropped to three-week lows on the news of the delivery, while the cost of insuring exposure to Turkish sovereign debt also rose. "As long as they meet the criteria, of course we are considering the procurement of the Patriots to cover our need for a long-range air and missile defense system".
It was not immediately clear when the system would be installed and activated for use.
Washington has already started the process of removing Turkey from the F-35 program, halting training of Turkish pilots in the United States on the aircraft.
American Lawmakers from both sides of the aisle have opposed Turkey having both the S-400 system and F-35 jets.
Global relations expert Soli Ozel of Istanbul's Kadir Has University points out that, with both Democrats and Republicans united in Congress on taking a tough stance against Turkey on the S-400, he thinks Ankara is miscalculating.