Russia and India are committed to adhering to timelines and other obligations under the S-400 missile deal, Russian ambassador Nikolay Kudashev said on Wednesday amid apprehensions of possible US sanctions against New Delhi over procurement of the weapons systems.

The envoy also said that both Russia and India do not recognise bilateral sanctions as they are "illegal tools" of "unlawful and unfair" competition and pressure.

During his visit to India last month, US Defence Secretary Lloyd Austin said there was no discussion with Defence Minister Rajnath Singh on the possibility of American sanctions against India over its S-400 deal with Russia as there has been no delivery of the missiles.

At the same time, Austin urged all allies and partners of the US to avoid buying Russian equipment that may invite US sanctions.

"Together with India, we do not recognise bilateral sanctions as they are illegal tools of unlawful and unfair, should I say, competition, pressure and even blackmail. It was clearly stated by the two foreign ministers in the course of their exchange," Kudashev said.

"With regard to S-400 and broader agreements, both sides are committed to the agreed timelines and other obligations. This contract is being successfully fulfilled," he added.

The US has already imposed sanctions on Turkey under the Countering America's Adversaries Through Sanctions Act (CAATSA) for purchase of S-400 missile defences from Russia.

Kudashev also said that the world order should be free from "unilateral approaches, illegal sanctions, double standards" and interference in domestic affairs of sovereign states.

"Collective international law based solutions should prevail over zero-sum games," he said, in his initial statement.

Ahead of Austin's high-profile India visit, Senator Robert Menendez, Chairman of the powerful Senate Foreign Relations Committee, in a letter urged the US Defence Secretary to take up with Indian leaders the issue of New Delhi procuring Russian S-400 missile defence system.

In October 2018, India had signed a USD 5 billion deal with Russia to buy five units of the S-400 air defence missile systems, despite a warning from the Trump administration that going ahead with the contract may invite US sanctions.

India made the first tranche of payment of around USD 800 million to Russia for the missile systems in 2019. The S-400 is known as Russia's most advanced long-range surface-to-air missile defence system.

Following the US sanctions on Turkey, there have been apprehensions that Washington may impose similar punitive measures on India.

The supply of S-400 missiles to India by Russia is expected to begin later this year.