Amid a campaign by the United States to undermine Russian arms exports, part of the Western bloc’s overall efforts to exert maximum pressure on and further isolate Moscow, the U.S. has threatened economic sanctions against a number of major clients for Russian arms. The proliferation of advanced Russian long range air defence systems has been singled out in particular, with key figures in the U.S. leadership attesting to the ability of such weapons systems to deny Western air assets access to certain airspace and thus their "freedom to dominate" theatres of their choice - a highly prized asset key to the Western bloc’s success in recent war efforts in Libya, Iraq, Yugoslavia and elsewhere. As a result states such as Turkey, Iraq, Myanmar and India which have considered acquiring Russia’s most advanced long range air defence platforms have increasingly come under threat of economic reprisals from the United States. India in particular, though prised as a key Western partner to contain the growing influence of China, has roused a great deal of concern in the Western bloc as a result of its intention to acquire Russia’s S-400 long range surface to air missile platform, and Delhi has recently concluded negations with Russia regarding the system's purchase. This missile system is considered the most advanced in the world of its kind, far surpassing Western analogues in their capabilities, and is capable of targeting and destroying even advanced stealth aircraft which the U.S. Air Force has come to rely on particularly heavily to operate. While India’s S-400 will provide a key asset in limiting the freedom of action of China’s growing stealth fleet, with the country being the only one to have designed and inducted into service a fully capable stealth fighter other than the United States and fielding these fighters in rapidly growing numbers, the proliferation of the Russian air defence technology to India is nevertheless viewed as highly undesirable by Washington. Washington has threatened Delhi that should it proceed to acquire advanced Russian hardware, the S-400 in particular, America would limit its defence cooperation with the South Asian state. While Russia is today by far India’s largest source of arms imports, and Moscow was a close defence partner throughout the Cold War, the U.S. hopes to press Delhi into swiftly cutting these longstanding defence ties. This will serve there purposes: further isolating Moscow internationally, starving Russia’s defence industry of a key source of revenue and pushing India out of its longstanding non aligned stance and further into the Western sphere of influence. Chairman of the U.S. House Armed Services Committee William Thornberry has noted that India’s planned acquisition of the S-400 would limit U.S. defence cooperation with India, and would also very likely cost the Indian military the right to acquire advanced U.S. hardware such as Predator drones - in which Delhi has shown a great deal of interest. He further noted that there was “a lot of concern in the US administration and Congress with the S-400.” The Chairman also threatened that India’s ability to jointly manufacture the F-16 single engine light fighter, a contract currently under negotiation, would likely be compromised should Dehli acquire the Russian weapons system. These threats, forcing India’s defence sector to choose between the United States and Russia, are set to potentially have a lasting effect on Delhi’s geopolitical alignment, forcing the country to reconsider its non aligned stances by denying it the ability to cooperate militarily with both power blocs. While Chairman Thronberry noted that India would most likely not come under direct economic sanctions as a result of the acquisition of the S-400, something other potential clients for the system such as Turkey have been threatened with, it was repeatedly stressed that this was conditional on India continuing to reduce its reliance on Russian arms. The threat of economic sanction remains however, and should India fail to meet U.S. requirements to further cut defence cooperation with Russia over time or should the military see in it its best interests to acquire Russian arms over their Western made counterparts, sanctions could very likely be applied in future. How Delhi will respond to U.S. threats, and whether America will succeed in cutting Russia off from one of its most critical and oldest defence partners or simply further alienate India, remains to be seen.