South Korea has announced an expansion of its air defence zone following China's move to establish a similar zone.
South Korea earlier requested China to redraw its air defence zone because it partly overlaps with South Korea's, but Beijing rejected it.
The US, Japan and other countries have also protested the Chinese zone.
Beijing said last month that all aircraft entering the vast area must identify themselves and follow Chinese instructions.
US, Japan and South Korea have flown military reconnaissance flights in the area without notifying China in defiance of Beijing's announcement.
The new South Korean zone covers a submerged reef that South Korea controls but that China also claims, and it enlarged parts of airspace also included in the Chinese zone.
The new South Korean zone also overlaps with parts of the Japanese air defence zone.
Defence Ministry spokesman Kim Min-seok told reporters that South Korea will discuss with neighbouring countries steps to prevent accidental clashes within the South Korean zone.
He said that South Korea's zone did not infringe upon any country's airspace and that Seoul had sufficiently explained its action to its neighbours before the announcement.
The US State Department supported South Korea, saying its approach "avoids confusion for, or threats to, civilian airlines".
"The United States has been and will remain in close consultation with our allies and partners in the region to ensure their actions contribute to greater stability, predictability, and consistency with international practices," State Department spokeswoman Jen Psaki said.
