Taiwan rejected on Tuesday a Chinese request to allow commercial planes to fly over the Taiwan Strait dividing the island and China to help ease commercial air congestion between the two sides.
The Defense Ministry said commercial planes should continue to fly either north or south of the 100-mile (160-kilometer) wide strait, reserving the area to the east of the median line for Taiwanese warplane training.
"National security will remain our top concern because the Chinese communists have refused to renounce the use of force against Taiwan or redeploy their troops" despite the recent easing of tensions, the ministry said on its Web site.
Since taking office 14 months ago, Taiwanese President Ma Ying-jeou has moved aggressively to improve relations with China. His administration inaugurated direct air and shipping links and eased conditions for two-way investment, hoping the steps could help stimulate the island's economy.
The two sides launched 108 weekly flights last December and agreed in April to increase the frequency to 270 flights a week. Last week, China's Taiwan Affairs Office chief Wang Yi proposed opening up the median line of the strait to help ease congestion, especially on northern routes.
Several Taiwanese lawmakers warned the proposal could be a Chinese ploy to undermine the island's defenses.
Taiwanese media says that throughout Ma's presidency China has continued intensive military exercises at coastal bases facing the island.
China and Taiwan split amid civil war in 1949. The communist mainland still views the democratic island as part of its territory, to be brought back into the fold by force if necessary. The Defense Ministry says China has some 1,300 missiles aimed at Taiwanese targets.