Negotiations have stalled for the double-tracking of congested air routes linking South Korea and Chinese and European cities amid the lukewarm attitude by Beijing due to the missile row between the neighbors, officials here said Thursday.

China has been retaliating economically against South Korea for the past few months over Seoul's deployment of the US missile defense system THAAD on its soil despite Beijing's strong objection.

South Korea says the missile defense system is not aimed at China but is to combat North Korea's missile and nuclear threats.

China, however, sees it as a national security threat.

China has not yet responded to South Korea's request to reopen talks for increasing traffic of the air corridor since early this year when the missile row erupted in earnest, an official of the Ministry of Land, Infrastructure and Transportation said.

Seoul and Beijing signed a memorandum of understanding late last year for the establishment of a task force headed by director-level officials of the two sides to discuss improving the air routes to ease congestion, the official said.

Air traffic to and from China and Europe has increased by 30 percent this year alone, according to ministry statistics.

Double-tracking the air routes linking South Korea to China and Europe will help increase the number of flights that can fly the routes as Seoul and Beijing currently fly only one flight every 10 minutes due to the congestion on the single track airway, industry sources said.

"We will try to make headway in talks with Beijing to minimize flight delays and secure air traffic safety in the congested sky over Beijing where more than 1,000 flights fly every day," a ministry official said. (Yonhap)