The first parts of a Russian S-400 missile defence system were delivered to Turkey on Friday, Ankara said, a development set to escalate tensions with the United States which has warned of sanctions over the deal. The S-400 consignment was delivered to the Murted Air Base outside the capital Ankara, the defence ministry said in a statement. "The delivery of parts belonging to the system will continue in the coming days," Turkey's Defence Industry Directorate said separately. "Once the system is completely ready, it will begin to be used in a way determined by the relevant authorities." President Recep Tayyip Erdogan said after meeting Donald Trump at the G20 summit last month that the <a href="https://www.thenational.ae/world/europe/erdogan-says-trump-promised-no-sanctions-over-russian-missiles-1.880698">US did not plan to impose sanctions on Ankara</a> for buying the S-400s. Mr Trump said Turkey had not been treated fairly but did not rule out sanctions. Turkish officials have repeatedly dismissed US calls to cancel the S-400 purchase, saying it was a "done deal". "We say this each time. This is a done deal," Foreign Minister Mevlut Cavusoglu told reporters in Ankara on Friday. "The process continues. We are coordinating this work, whether permission for planes, personnel. "There are no problems, the process will continue in a healthy manner." The United States says the S-400s are not compatible with Nato's defence network and could compromise its Lockheed Martin F-35 stealth fighter jets, an aircraft Turkey, a Nato member, is helping to build and planning to buy. A press briefing on Turkey accepting the delivery of a Russian missile defence system was postponed by the Pentagon on Friday. Senior leaders were scheduled to have briefed journalists on the US response. Acting US Defense Secretary Mark Esper had spoken with his Turkish counterpart for about 30 minutes on Friday but the Pentagon had provide no details on what was discussed. Under possible US sanctions, Turkey could face expulsion from the F-35 programme, a move Mr Erdogan has dismissed. But Washington has already started the process of removing Turkey from the F-35 programme, halting training of Turkish pilots in the United States on the aircraft. Under legislation known as Countering America's Adversaries through Sanctions Act (CAATSA), which targets purchases of military equipment from Russia, Mr Trump should select five of 12 possible measures. These range from banning visas and denying access to the US-based Export-Import Bank, to the harsher options of blocking transactions with the US financial system and denying export licences. A Nato official reiterated the alliance's concern about Turkey S-400 purchase after Ankara announced the arrival of the first shipment. "We are concerned about the potential consequences of Turkey's decision to acquire the S-400 system," the official said. "Interoperability of our armed forces is fundamental to Nato for the conduct of our operations and missions." At least two Russian Air Force AN-124 cargo planes flew to Turkey on Friday morning, data from plane tracking website Flightradar24 showed. Turkish broadcasters showed footage of one plane parked at airbase and a second one landing at around 12.30pm. Russia's Federal Service for Military-Technical Co-operation confirmed 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.