WASHINGTON ― Russian officials expect to sign a deal with India for Russia’s S-400 surface-to-air missile defense system, according to Interfax news agency.

“I think that in the current year we will sign the corresponding contract document,” Interfax quoted Dmitry Shugaev, the head of the Federal Service for Military-Technical Cooperation, as saying.

All technical aspects of the deal have reportedly been agreed upon, but the price tag is still under negotiation.

The S-400 Triumf is one of Russia’s most advanced air defense systems. It is currently deployed in the Russian enclave in Kaliningrad, recently annexed territory in Crimea and in Tartus, Syria, to protect Russian and Syrian air and naval units. The system is also deployed throughout western and eastern Russia.

Over the past several years, Russia has been marketing the S-400 to a variety of potential buyers.

After a long and drawn out saga, Turkish officials confirmed in December 2017 that Ankara and Moscow had signed a contract for at least one S-400 system, with delivery expected by early 2020. In November 2014, Russia agreed to sell China four to six S-400 battalions. The first units began to arrive in China in January 2018.

It was reported in 2016 that India and Russia agreed to a sale of five S-400 systems, worth approximately $5.5 billion. However, it is unclear if any S-400s have been delivered to India.

Russia and India have a history of collaborating and sharing missile technology. Not only does India currently operate the Russian-made S-300 ― the S-400’s Cold War predecessor ― but the two countries also partnered throughout the late 1990s and 2000s to develop the BrahMos anti-ship and land attack cruise missile.