Even as the U.S. has reiterated its reservations about Turkey and India’s purchase of the S-400 missile system, Indian and Pakistani military experts believe that it was the best available air defense system in the world.

Axar.az reports citing foreign media that they maintained that American alternatives at present were no match to this tested Russian system.

Former Deputy Chief of Indian Air Force (IAF) Kapil Kak and ex-Director General of Pakistan’s powerful Inter-Services Intelligence (ISI) Gen. Ehsanul Haq told Anadolu Agency that the U.S. attempts to foist its interests on sovereign countries, would prove counterproductive. Both of them believed that the U.S. behavior was in a way an attack on the strategic autonomy of these countries.

“My view is that Turkey and India will very jealously protect autonomy in their strategic decision making. They will find it very difficult to align with the U.S. dictate on the S-400 issue. The U.S. administration should find a diplomatic solution to the issue and retain its political and military linkages with Turkey,” said the former ISI chief.

A U.S. government official on Monday warned against purchase of the Russian equipment while speaking to Indian journalists in Washington ahead of an expected visit by U.S. Secretary of State Michael Pompeo to New Delhi as part of preparations to arrange a meeting between U.S. President Donald Trump and Indian Prime Minister Narendra Modi on the sidelines of the G-20 summit in Japan later this week.

“With respect to S-400, we are urging all our allies and partners, India included, to forgo transactions with Russia that risk triggering CAATSA (Countering America’s Adversaries Through Sanctions Act) ... This is a time we will be encouraging India to look at alternatives,” said the official, according to Indian media reports.

Retired Air Vice Marshall Kapil Kak, who has commanded fighter jets and is involved in strategic planning in India, said in terms of tracking and scanning of radars, height parameters and the area it can cover, the S-400 system was the best in the world. He said the U.S. offer to supply American Patriot missile defense system was not an alternative to match their strategic requirements.

“My back up on calculation is that S-400 is superior than any other system, be that the American Patriot. It also depends on Patriot derivate that is on offer. For S-400, we know exactly what it means. We are not sure, when Americans talk us about Patriots. It has been used in the Gulf war and upgraded subsequently. But as far as the configuration, we know, it is not superior to S-400. I do not think, it will either interest Turkey or India,” said Kak, who has also served as chief instructor at the Defense Services Staff College at Wellington, the capital of New Zealand.