South Korea had objected to China’s November 23 move as unacceptable because its new zone includes a maritime rock named Ieodo, which Seoul controls, with a research station platform built atop it. China also claims the submerged rock.

But South Korea’s reaction to Beijing has been more measured than the sharp rebukes delivered from Tokyo and Washington, reflecting a sensitivity towards Seoul’s largest trading partner.

South Korea’s air defence zone was originally established by the U.S. Air Force in 1951 during the Korean War. The extension of the zone will not apply any restrictions to the operation of commercial flights, the defence ministry said separately in a statement. The move will take effect on December 15, it said.

It will also result in an overlap with Japan’s air defence zone, Jang said.