The statement comes after reports suggested India will receive a blanket waiver.
The US official insisted that there is no country-specific blanket waiver for such a major defence purchase instead there will be a "case-by-case analysis" on the sanctions mandated under the US legislation.
The statement also suggested that sanctions under countering America’s adversaries through the sanctions act known as Countering America's Adversaries Through Sanctions Act(CAATSA) could be applied.
CAATSA imposes sanctions on nations engaging in “significant transactions” defined as any purchase above $15 million with the Russian state-owned defense industry.
However, the statement also added that the Trump administration does not want to make a decision that degrades the defence capabilities of India. The US had recognised India as a "major defence partner" in 2016.
New Delhi had announced its plans to purchase Russia’s S-400 missile systems back in 2015. The $5.43 billion worth S-400 contract was signed during Russian President Vladimir Putin’s visit to India last year.
The US had earlier said it was "very upset" about Turkey's purchase of Russian missile defence systems and could impose sanctions on Ankara if it does not "get rid" of them.
The head of Turkey's Defence Industry Directorate had said last year that a second S-400 delivery to Turkey may be delayed beyond a planned 2020 timeline by talks on technology sharing and joint production.
After the Erdgoan regime brough the missile system from Russia, Washington removed Turkey from the F-35 programme, in which Ankara was a manufacturer and buyer.
The S-400 is the most advanced long-range air defense missile system that had gone into serive in Russia in 2007.
The defence system is designed to destroy aircraft, cruise and ballistic missiles, including medium-range missiles, and can also be used against ground installations.
The S-400 can engage targets at a distance of 400 km and at an altitude of up to 30 km.