Russia will begin S-400 missile system deliveries to Turkey in 2019 - a year earlier than previously announced.
The move comes amid a growing rift between Turkey and its NATO allies in the West.
"The contract on the S-400 to Turkey is being executed within the agreed timeline," said Alexander Mikheyev, chief of Rosoboronexport, Russia's state weapons exporter.
"In 2019, we will begin to fulfil this contract," Interfax news agency cited him as saying on Tuesday.
Last year, the chief executive of S-400 manufacturer Rostec said the missile system deliveries would start in 2020.
Rosoboronexport also said it would switch to using local currencies in deals with foreign trade partners instead of using the US dollar, RIA news agency reported.
$2.5bn deal
Turkey will be the first NATO member state to acquire the advanced Russian surface-to-air missile system in a deal worth $2.5bn, Rostec's Sergei Chemezov told Russian newspaper Kommersant in December.
The S-400 system, incompatible with NATO systems, is touted as being able to engage aerial targets within a 400km range.
US military officials and politicians have expressed concerns over Turkey's intention to buy the Russian missile system.
The United States in recent weeks imposed sanctions against Turkey in an effort to effect the release of a US pastor allegedly linked to plotters of the country's failed 2016 military coup.
The sanctions have played a role in sending Turkey's economy into a tailspin.
