Doval was tasked with convincing the trump administration that the S-400 deal does merit a United States presidential waiver from the provisions of the Countering America's Adversaries Through the Sanctions Act (CAATSA). In recent years, the USA has also become a significant source, with purchases adding up to $15 billion over the past decade.
The S-400 system, which is effective against aircraft as well as ballistic and cruise missiles, has a maximum range of 250 miles.
One of the announcements would be holding of the joint India-Russia counter-terrorism exercise, Indra-2018, set to be held from November 18 to 28, 2018.
But the U.S. considers India a strategic ally and therefore a waiver may be issued.
"As and when the government approves it, delivery (of the missiles) will be in 24 months", Indian Air Force chief B.S. Dhanoa had earlier said.
The US has urged its allies to forgo transactions with Russia, warning that the S-400 missile defence system that India intends to buy would be a "focus area" for it to implement punitive sanctions against a nation undertaking "significant" business deals with the Russians.
In talks with USA officials, India has stressed its need for the air defense system to strengthen its capabilities against the might of China, whose ambitions are moving New Delhi and Washington closer.
Indian Air Force Chief BS Dhanoa had said on Wednesday that Rafale aircraft with France and the S-400 air defence missile system deals with Russian Federation are like a "booster dose", according to The Indian Express. "I am very happy that you have assured full cooperation of Russian Federation in this mission", Modi said. Various U.S. officials, including U.S. Secretary of Defense James Mattis, have openly spoken out against possible sanctions on India.
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S-400 defence system is expected to boost India's defence along the country's borders with neighbours Pakistan and China. It will cost India $5 billion (over Rs 40,000 crore), making it the country's largest defence deal .
"In today's fast-changing world, our relationship assumes heightened importance", Modi told Putin.
Russian Federation and India denounced terrorism in all its forms and manifestations and reiterated the need to combat global terrorism with decisive and collective response without any double standards, the statement said.
China has already been affected by the sanctions for buying weapons from Russian Federation, including the S-400.
The S-400 surface-to-air missile system is capable of tracking and taking down aircraft hundreds of miles away, and India believes it needs it to defend the country against not only China but also Pakistan.
India has also been irked by Trump's decision to exit from the 2015 nuclear deal between major powers and Iran, a major supplier of oil to the fast-growing Indian economy.
Russian Federation has been one of India's key suppliers of arms and ammunition.
Jinnie Lee, a spokeswoman for the US Embassy in New Delhi, declined to comment on whether India would be granted a waiver, but said in a statement that the sanctions were "not meant to impose damage to the military capabilities of our allies or partners".