Under the trade agreement, India will buy the cutting-edge S-400 missile systems from Russia to boost its military prowess.
The “next-generation” units can destroy aerial targets from up to 248 miles (400km) away, according to Russian state media.
Indian officials want the systems to counter the ballistic missiles and stealth aircraft being developed by China.
Defence chiefs in Moscow hope to confirm the deal in October, when Russia and India are due to hold a bilateral summit.
Dmitry Shugaev, who oversees Russia’s arms exports, said: “As for the S-400, we have already prepared everything to sign this contract.
“All the main technical and commercial aspects have been agreed upon, and I think that we are close to making this happen.
“We hope to sign both contracts with our Indian partners by the end of the year.
“If we sign the deal until the end of this year, I think the deliveries to India will be possible in 2020.”
Mr Shugaev said Moscow had agreed to lower the price after considering the “strategic partnership” between Moscow and New Delhi.
He said: “India is a strategic partner for us, so we took into account the wishes of our partners, and made certain concessions.”
The deal was first proposed during a meeting between Russian president Vladimir Putin and Indian leader Narendra Modi in 2016.
It was recently reported that Russia and India were planning to jointly design a fifth-generation fighter jet.
But the Russian official revealed the proposals are on hold, telling Sputnik: “It is frozen for now.
“But we hope that we will return to the dialogue on the fifth-generation fighter.”
His comments came after India‘s commerce minister hailed the “time-tested relations between the two countries”.
Speaking an aviation event in New Delhi, Suresh Prabhu said: “India is full of opportunities for the expanding aviation industry.
“Both India and Russia can together work to change the present aviation scenario.”