Turkey, Russia discuss new S-400 supplies: report
Alexander Mikheyev, head of state arms exporter Rosoboronexport, told Interfax news agency that the two countries were discussing financing and "a delivery schedule".
He did not provide further details on the ongoing talks.
In July, NATO member Turkey received the first batch of Russia's S-400 missile defence systems in a move that raised tensions with the United States.
In response, Washington kicked Turkey off its F-35 fighter jet programme.
The US says Russia will be able to glean sensitive technical knowledge about the new fighter if it is operated alongside the S-400.
Moscow and Ankara have made much of their defence and political cooperation.
This week, Russia and Turkey agreed to ensure Kurdish forces withdraw from areas close to Syria's border with Turkey and to launch joint patrols.
The agreement cemented Russia and Turkey's roles as the main foreign players in Syria, after US President Donald Trump announced the withdrawal of American forces from the country's north earlier this month.
