South Korea said on Sunday it plans to expand its air defence identification zone to cover an area of ocean contested with China, in response to Beijing's recent move to create an air defence zone in the East China Sea.
The South Korean zone will incorporate airspace above a submerged rock claimed by both Beijing and Seoul that falls within China's zone. The move was widely expected and will take effect on 15 December.
Beijing's establishment late last month of a new air defence zone angered the US and Japan, which see it as a step to assert China's control of the East China Sea area and bolster its claim to islands administered by Tokyo.
Seoul also raised objections because the new Chinese zone overlaps South Korea's air defence zone and covers a submerged reef called Socotra Rock. South Korea and China have for years contested the rock, known as Ieodo in South Korea and Suyan in China, and economic rights to the ocean area around it.
South Korea built a nautical research station on the rock in 2003, giving it effective control. It lies southwest of the Korean peninsula, about 105 miles from the nearest South Korean land territory and 180 miles from the closest Chinese land.
In November, Seoul called on Beijing to redraw its air defence zone to reflect its concerns. After the demand was rejected, South Korea said it would consider expanding its own zone.
The move to proceed is unlikely to significantly raise tensions in the region. China has reacted calmly to the South Korean plans, which have also been accepted by the US and Japan.
In Beijing, on Friday, a Chinese foreign ministry spokesman said South Korea should observe international law in expanding its air defence zone, but said it didn't affect maritime claims because the zones are designed only to identify aircraft outside territorial airspace.
"South Korea should be in line with international laws and conventions. China will stay in communication with South Korea," said the spokesman, Hong Lei.
US Vice President Joe Biden and South Korean President Park Geun-hye discussed South Korea's plans to extend its air defence zone in a meeting in Seoul on Friday. A senior US official said Biden has "expressed understanding" for South Korea's approach.
The expansion also overlaps Japan's air defence zone but doesn't cover any Japanese territory. A spokeswoman for Japanese Prime Minister Shinzo Abe said the Korean move didn't pose a problem for Tokyo because Seoul made clear the zone wouldn't infringe on the freedom of travel by commercial planes.
"Unlike the Chinese action, we reached an understanding beforehand, so this would not create an immediate problem for Japan-Korea relations," Hikariko Ono said.
South Korea's defence ministry played down the possibility of airborne clashes or accidents because of the extended South Korean zone.
"We will coordinate with related countries to fend off accidental military confrontations and to ensure safety of airplanes," defence ministry spokesman Kim Min-seok said.