A senior US official has left open the possibility that Washington may not impose sanctions on India for buying the Russian Triumf S-400 missile defence system but require New Delhi to tighten defence technology security to prevent snooping by Moscow.

The State Department official, who addressed Turkey buying the Russian S-400 missile defence system, did not directly address India acquiring the same system when it was raised during a briefing on Thursday butbrought up security issues in cooperating with India.

The State Department approved the USD billion sale ofadvanced MK 45 5 inch/62 caliber (MOD 4) navy guns to India this week eventhough India had paid the Russian contractor $800 million as an advance inAugust for five S-400 units valued at about $5.4 billion.

This and the official`s response appeared to leave room forIndia to get a waiver from the Countering America`s Adversaries ThroughSanctions Act (CAATSA), which could be applied to India for buying equipmentfrom Russian companies. CAATSA bans countries from buying equipment worth morethan $15 million from defence Russian companies listed under it and imposessanctions against them.The US has not yet introduced CAATSA sanctions againstTurkey, a NATO partner, but has refused to provide it with the advanced F-35stealth combat jets.

India is not seeking such advanced armaments from the US atthis time.

President Donald Trump warned Turkish President Recep Erdoganduring his recent visit that the Russian deal is going to put it at risk ofsanctions.But the official said: "The timeline on CAATSA sanctions is notprescribed or absolute. There is still plenty of scope that could be applied asto where sanctions and the breadth and depth of sanctions could be imposed uponTurkey."

The official appeared to appreciate the problems India facesin moving away from Russian defence supplies because of its decades-longdependence on the Soviet Union.The official said that when Secretary of StateMike Pompeo and another official visited New Delhi they "had a consistentline and a discourse with our Indian counterparts at our respective levels,which is we recognize how India suffered at the fall of Soviet Union" becauseof its dependence on it for defence equipment.

The official added, "It was catastrophic if one wasserving in the Ministry of Defence in India in the early 1990s. So we getthat."The official said that India should take stringent measures to preventdefence technology leakage.

US industry and the government are interested inco-research, co-development and co-production with India in the defence sector,"but we can`t do it in a fashion that will expose us as well as ourindustry," the official said."So for India, yes, there`s anopportunity, but they have got to address their protocols and their processeson protecting defence technology and procurement processes," the official.

"What we have pushed with Indians is: tighten up yourprocurement processes, tighten up your defence technology security processesand protocols, and then you`re putting yourselves in a much more mature spaceto be a tighter, closer partner," the official said.

The official added that the US didn`t want its technology"exposed because some Russians walking the shop floor decide to go, walkaway and put it in their handbag or knapsack and take it back to Moscow. We`renot going to allow that."

Last year India and the US signed the CommunicationsCompatibility and Security Agreement (COMCASA) to "facilitate access toadvanced defence systems and enable India to optimally utilise its existingUS-origin platforms."