Japan has dispatched its biggest warship to guard a US supply vessel approaching one of its islands for refuelling. The move comes after North Korea threatened to sink the US Navy's supercarrier USS Carl Vinson and its nuclear-powered submarine USS Michigan.

The supply ship – part of the USS Carl Vinson-led armada heading to the Korean peninsula – will be guarded while it sails on Monday (1 May) from waters off the Boso Peninsula in Chiba Prefecture to the area off Shikoku, government sources told the Japan Times. The armada reportedly entered the Sea of Japan over the weekend.

The move, ordered by Japanese Defence Minister Tomomi Inada, was reportedly the first by the government after it passed a controversial security law in 2016 expanding the role of its military. The law that came into force in March 2016 enables the government to order its military to perform peacetime exercises like protecting forces and equipment of allies, in addition to undertaking the usual "collective self-defence" tasks.

The primary mission of the 249-metre-long Izumo-class warship, which can operate up to nine helicopters, is anti-submarine warfare, the paper wrote. It added that the carrier is as big as Japan's World War II-era warships. The Izumo warship that was dispatched for the protection of the US vessel was based in Yokosuka sea port in Kanagawa Prefecture, which is also home to the aircraft carrier USS Ronald Reagan.

Japanese warship Izumo
Japan Maritime Self-Defence Force's latest Izumo-class helicopter carrier DDH-184 Kaga is seen at a port in Yokohama Reuters

Japan recently concluded naval exercises with the US armada in the wake of escalating tensions in the Korean peninsula, with North Korea continuing its missile launches despite objections from its neighbours and the western world.

The reclusive state, led by Kim Jong-un, conducted a failed missile test on 29 April further angering its adversaries as well as its longtime ally China.

US President Donald Trump called Kim a "cookie" and said the latest missile launch was "disrespectful" towards the Beijing administration, which reportedly urged Pyongyang to stop engaging in provocative acts. China has already threatened North Korea with unilateral sanctions if it did not stop its nuclear tests.