S-400
US expresses 'concern' over delivery of Russia's S-400 missile system to India
The S-400 is known as Russia's most advanced long-range surface-to-air missile defence system
US warn Turkey of facing 'very negative' consequences over S-400 deal
Turkey has repeatedly rejected US ultimatums for cancelling S-400 shipments and the purchase of American Patriot batteries instead.
'Heard, Understood' by US: Sitharaman on Indo-Russian missile deal
US President Trump's administration imposed sanctions on China's military over Beijing's purchase of the S-400 and other military hardware.
Trump’s sanction regime
The US will either have to come to a reasonable negotiation of the matter with Iran or go ahead and sanction India.
Just not defence, new improved S-400s can hit back
President Trump's comment that India will find out about the US reaction to the purchase
Getting US sanctions waiver for S-400 missiles not easy for India: Experts
Under CAATSA, India is subject to sanctions now as it has entered into agreement with Russia to buy S-400 Triumf missiles.