S-400 (image: alaraby.co.uk)

The United States is working with India to offer an alternative to the Russian S-400 Triumf missile defence system, but it ruled out the possibility of the country punishing India if it chooses the Russian systems, Assistant Defence Secretary Randall Schriver said Wednesday.

"I think it would be an unfortunate decision if they chose to pursue that", he told the House of Representatives Armed Forces Committee in Washington during a hearing on US Military Activities in Indo-Pacific region.

"We are very keen to see them make an alternative choice and we're working with them to provide potential alternatives,” he said.

India agreed to buy four S-400s for nearly $5.9 billion (INR 40,000 crore) in October last year. India went ahead to seal the deal notwithstanding the US' warnings against it. America imposes secondary sanctions known as Countering American Adversaries Through Sanctions Act (CAATSA) against countries that buy Russian military equipment. The CAATSA was passed to punish Russia for its interference in US elections and its involvement in Ukraine.

"We want to work through it. The legislation (CAATSA) is not designed to be an impediment in the growing strategic partnership we have with India. It's designed for consequence to Russia," Schriver said.

Possible US alternatives to the Russian S-400 are the Lockheed Martin's THAAD system (short for Terminal High Altitude Area Defense) and Raytheon's Patriot system, although the three vary in capabilities and costs.

The US is also persuading Turkey, its NATO ally, to drop the S-400 deal and purchase Raytheon’s systems.