(CNN) -- In a move that is certain to anger China, South Korea has expanded its air defense zone to include an area claimed by both countries.
Last month, China declared an Air Defense Identification Zone (ADIZ) in the East China Sea and declared that planes flying through it needed to file flight plans.
The Chinese zone covers a disputed submerged rock in the Yellow Sea, known by Korea as Ieodo and by China as Suyan.
Thumbing its nose at China's flight plan demand, South Korea first sent planes into the area without notifying China.
And on Saturday, it expanded its air defense zone to include the rock. The new zone will go into effect on December 15.
South Korea Defense Ministry spokesman Kim Min-seok said the move was in accord with international norms.
"The new KADIZ's southern region was adjusted so that it is in line with Incheon Flight Information Region, which is internationally used (recognized) and does not overlap with that of neighboring countries.
"The adjusted region includes airspace over Ieodo waters and Marado and Hongdo islands which is our territory."
China didn't immediately respond to the South Korean move.
But a spokeswoman for the State Department said Seoul had consulted with the United States ahead of time.
"We appreciate the ROK's efforts to pursue this action in a responsible, deliberate fashion by prior consultations with the United States and its neighbors, including Japan and China," spokeswoman Jen Psaki said.
John Delury, an assistant professor of East Asian Studies at Yonsei University, said he did not think the situation would likely escalate.
"I see no reason why the new zone will cause military dispute. I think this is a manageable situation. Neither side wants a military conflict," Delury told CNN. "I think the two sides can manage it if they want to - having overlapping zones is not necessarily the end of the world."
He said China's relatively low-key comments had stressed that it had no territorial dispute with Seoul over the submerged rock.
"They may be exploiting an ambiguity because it's not an island, so there can't be a territorial dispute," he said. "(But) I think they are trying to downplay (it), they are not trying to pick a fight with South Korea. They are clearly in fight with Japan."
Ties between China and Japan, always tense due to regional rivalry and lingering bitterness from World War Two, have been strained for months by the dispute over the islands in the East China Sea, called the Diaoyu by China and the Senkaku by Japan.