Russia and Turkey are in an advanced stage of discussion on the delivery of the second S-400 batch, but the agreement has not yet been signed, Dmitry Shugaev, head of Federal Service of Military-Technical Cooperation, said on Sunday.
"We are awaiting for the decision of the Turkish partners to sign another option contract", Shugaev said in an interview with Zvezda TV.
Earlier, the general director of Rosoboronexport, the Russian agency dealing with the import and export of defence-related products and services, stated that Moscow and Ankara had signed a contract for the supply of a second batch of S-400 air defence systems to Turkey.
"We are currently engaged in talks on the financial model for the execution of this contract with our partners", Mikheev told reporters during the Army-2020 forum.
The Turkish defence industry head, Ismail Demir, previously said that Moscow and Ankara had reached an agreement in principle on the supply of the second batch of S-400s.
The two countries signed a loan agreement on the delivery of S-400 systems in December 2017. In 2019, Turkey received several S-400 battalions worth $2.5 billion.
Washington has been opposing the agreement and demanded that Turkey ditch the S-400s and purchase US Patriot systems instead. The US also threatened to delay or even cancel the sale of F-35 fighters to Turkey and slap sanctions against Ankara, claiming that the Russian systems are incompatible with the NATO standards and pose security concerns.
Both Ankara and Moscow dismissed the allegations and continued negotiations on an additional batch of S-400s.