India will receive the systems on time, at the agreed date and without any delays, Russia's deputy foreign minister Sergey A Ryabkov told journalists.
In a statement, the Foreign Office said the Indian purchase was part of its efforts to acquire a Ballistic Missile Defence (BMD) System through multiple sources.
Responding to questions on reports that India will continue to purchase oil from Iran after November 4, State Department spokesperson Heather Nauert said this was "not helpful".
Describing the S-400 missile deal as the "largest contract" in the history of Indo-Russia ties, Nikolay Kudashev said it was one of the speediest pacts to be signed between the two countries.
Dhanoa said it is the duty of the Air Force personnel to remain combat worthy and maintain combat systems operational for any contingency at a short notice.
The 19th summit held in New Delhi recently can be considered a milestone in the history of bilateral summits that have been taking place since 2000, Sreenivasan said.
India and Russia signed a multi-billion-dollar deal to procure the S-400 Triumf air defence system, which could attract sanctions under the Countering America's Adversaries Through Sanctions Act.
Under the CAATSA, India is subject to sanctions now that it has entered into an agreement with Russia to purchase S-400 Triumf missile defense system.
Responding to a query on impact of anti-Russia sanctions on India after the conclusion of the S-400 contract, the US embassy spokesperson said, it cannot prejudge any sanctions decisions.
India and Russia signed eight pacts on Friday, including on cooperation on Gaganyaan.