Turkey purchased four Russian S-400 air defense systems worth $2.5 billion with 55 percent of the sum under the contract being covered by Russian loans, CEO of Russia’s Rostec Corporation Sergey Chemezov told the Kommersant newspaper in an interview issued on Wednesday.

He confirmed that Ankara had bought four S-400 systems. “Yes, they bought four S-400 systems worth $2.5 billion,” Chemezov said.

He also pointed out that the Russian and Turkish Finance Ministries had already completed talks on Moscow’s loans for Ankara.

“They should finalize financial papers now. I can say, Turkey will pay 45 percent of the whole some in advance, while 55 percent is being funded by Russian loans. We are going to start deliveries in March 2020,” Chemezov added.

Earlier, Turkish President Recep Tayyip Erdogan said that the documents Russian S-400 had been signed and that Ankara wanted to take steps to implement the agreement as soon as possible.

The S-400 Triumf, previously known as the S-300PMU-3, is an anti-aircraft weapon system developed in the 1990s by Russia’s Almaz Central Design Bureau as an upgrade of the S-300 family. It has been in service with the Russian Armed Forces since 2007.

The S-400 uses four missiles to fill its performance envelope: the very-long-range 40N6 (400 km), the long-range 48N6 (250 km), the medium-range 9M96E2 (120 km) and the short-range 9M96E (40 km).

The S-400 has been described, as of 2017, as “one of the best air-defense systems currently made”.