In addition, Indian defense analyst, Ajai Shukla, told Al-Jazeera that "the United States has more or less indicated that it agrees with this project and is not likely to invoke sanctions against India as a result".
Moscow has long been India's largest supplier of military equipment, accounting for 62 percent of its total arms imports over the past five years, according to the Stockholm Peace Research Institute.
However, in recent years, New Delhi had moved closer to the U.S. and Israel in terms of new weapons.
The U.S. has issued threats to Turkey for the planned purchase of the same missile defense system.
Under a U.S. law, known as the Act to Counter U.S. Adversaries through Sanctions (CAATSA), the purchase of defense equipment from Russia may be subject to sanctions. However, the president may choose to issue an exemption.