Beijing has repeatedly protested the passage of US warships in the South China Sea, accusing Washington of violating Chinese sovereignty. Tensions between China and the US have recently further escalated in the wake of the protracted trade war and the blacklisting of Huawei.

Japan and the United States are conducting joint exercises in the South China Sea involving the USS Ronald Reagan, a nuclear aircraft carrier, as well as the JS Izumo, a Japan Maritime Self-Defence Force helicopter carrier, Sankei Shimbun newspaper reported on Wednesday.

According to the Japanese newspaper, the manoeuvres began on 10 June. Besides the JS Izumo, destroyers JS Murasame and JS Akebone are involved in the war games, with the warships mainly practising joint manoeuvring.

The USS Ronald Reagan, with a displacement of 101.4 thousand short tonnes, is one of the world's largest warships. It can carry up to 90 airplanes and helicopters of various types.

The JS Izumo, Japan’s most powerful surface combat vessel, has been on a long-term mission since the end of April, making port calls in Malaysia and Singapore.

The publication notes that the drills are tasked with the goal of countering China, which has laid claim to the South China Sea and is building islands there. Beijing remains embroiled in disputes with a number of countries in Southeast Asia that also have competing claims to areas of the sea zone.

China controls the vast majority of islands, reefs, and shoals in the South China Sea, and has been expressing concerns over the deployment of US vessels in the area, accusing Washington of violating its sovereignty.

In early May, China expressed its “strong opposition” after two US warships sailed near disputed islands in the South China Sea in a move the US says was aimed to “challenge excessive maritime claims”.

It was the third time this year that Washington challenged Beijing’s maritime claims in the region amid an escalating rivalry between the two powers in a protracted trade war which has involved other areas of conflict.

China’s sweeping claims of sovereignty over the sea , with its estimated vast reserves of untapped oil and natural gas—have antagonised competing claimants Brunei, Indonesia, Malaysia, the Philippines, Taiwan, and Vietnam.As early as the 1970s, countries began to claim islands and various zones in the South China Sea, such as the Spratly Islands, which possess rich natural resources and fishing areas.

The South China Sea is a major strategic passageway, with over $5 trillion worth of maritime cargo passing through the area annually.