During his address at the 11th East Asia Summit in September 2016, Modi said "the threat or use of force" to resolve dispute in the region would complicate matters affecting peace and stability.
On Saturday, Mattis said, "Respecting freedom of navigation and adhering to international norms [are] essential for peace and economic growth in the inter-linked geography of the Indo-Pacific."
"The US can't accept Chinese actions that impinge on the interests of the international community, undermining the rules-based order that has benefited all countries represented here today including, and especially, China," PTI quoted Mattis during his address to some 500 delegates at the Shangri-La Dialogue which focuses on defense and security issues in the region.
The US Defense Secretary also said that conflict with China is not "inevitable", but the two countries will engage in competition.
A Chinese foreign ministry spokesperson, however, termed Mattis' comments "irresponsible" and reiterating China's territorial claims over the disputed Spratly islands.
"China has indisputable sovereignty over the (Spratly) Islands and their adjacent waters," AFP quoted Hua Chunying, Chinese foreign ministry spokesperson as saying.
Chinese experts, however, have their own take on Indian and US positions in the South China Sea.
"China supports freedom of navigation across all oceans and seas and it should not just be limited to the South China Sea. In fact, we must defend freedom of navigation in the South China Sea as it is in our interest. China is the number one trading country in the world. But, freedom of navigation should not be considered synonymous to economic rights over exclusive economic zones," Long Xingchun, Associate Professor at the China West Normal University based in Nanchong, Sichuan province in China told Sputnik. Long is also a visiting professor at the University of Colombo.
China claims the entire South China Sea region as its own and is engaged in a bitter dispute with Vietnam, Malaysia, the Philippines, Brunei and Taiwan who also have counter claims. Beijing has built installations at strategically located islands in the region, which is considered to be rich in minerals, oil and other natural resources.