Defence Secretary James Mattis has expressed confidence that India and the US would be able to resolve all issues related to India's purchase of the S-400 air defence systems from Russia that could draw possible US sanctions. India risked US sanctions when it agreed in October to a USD 5 billion deal to buy Russian missile systems. India's purchase is subject to potential US sanctions under the Countering America's Adversaries Through Sanctions Act (CAATSA), which deals primarily with countries having "significant transactions" with Russia, North Korea or Iran. "We will work everything out. Trust me," Mattis told reporters Monday as a journalist asked the visiting Defence Minister Nirmala Sitharaman about the missile deal and the possibility of US sanctions. India needs a presidential waiver to get around the punitive CAATSA sanctions. READ ALSO |\u00a0Joint exercise between American and Indian Air Forces begin, fighters to roar in the skies for a fortnight "We'll work all this forward. This is the normal collaboration and consultation that we have with each other," Mattis said in response to a similar question. "India has been spent many, many years in its nonaligned status, and it's drawn a lot of weapons from Russia," Mattis told reporters at the Pentagon ahead of Sitharaman's arrival on Monday. Russia's S-400 system, a mobile long-range surface-to-air missile system, made its debut on the world stage in 2007. The platform rivals Lockheed Martin's THAAD, or terminal high altitude area defense, system and Raytheon's Patriot system. S-400 is known as Russia's most advanced long-range surface-to-air missile defence system. China was the first foreign buyer to seal a government-to-government deal with Russia in 2014 to procure the lethal missile system. Moscow has already started delivery of an undisclosed number of the S-400 missile systems to Beijing.