Russia has started delivering the S-400 Triumf surface-to-air missile systems to India ahead of President Vladimir Putin's visit to India next month. 

Director of the Federal Service for Military-Technical Cooperation (FSMTC) Dmitry Shugaev told Sputnik ahead of the Dubai Airshow. "The supplies of the S-400 air defense system to India have started and are proceeding on schedule." 

Russia and India signed a contract on the delivery of S-400s in October, 2018. In August, the head of Russia's state arms exporter Rosoboronexport, Alexander Mikheev, told Sputnik that negotiations on the supply of S-400 air defense systems were underway with seven countries in the Middle East, the Asia-Pacific region and Africa.

In October 2018, India had signed a $5 billion deal with Russia to buy five units of the S-400 air defence missile systems, despite a warning from the Trump administration that going ahead with the contract may invite US sanctions.

India made the first tranche of payment of around $800 million to Russia for the missile systems in 2019. The Hindu said. The S-400 is known as Russia’s most advanced long-range surface-to-air missile defence system.

Following US sanctions on Turkey over the procurement of S-400 missile systems, there have been apprehensions that the Russian missile system will increase India’s chances of coming under CAATSA (Countering America's Adversaries. In this context, Prime Minister Narendra Modi met with a high-power U.S. Congressional delegation in New Delhi over the weekend.  A statement from the Ministry of External Affairs (MEA) said the delegation led by Senator John Cornyn discussed issues related to the developments in South Asia and the Indo-Pacific region.

Three Republican Senators have already moved a bill to exempt India from possible CAATSA sanctions for taking the delivery of the S400 missile system. (SAM)