Philippine President Benigno Aquino III said Wednesday that his country would lease five TC-90 training planes from Japan to assist the Philippine navy in patrolling its claimed territory in the disputed South China Sea. On the same day, Manila's outgoing Air Force Commander Lt. Gen. Jeffrey Delgado was quoted by The Philippine Star as saying that the Philippines has purchased two newly refurbished C-130 Hercules planes from the US for its air force.

The Philippines, which remains one of the weakest militaries in the region, has to rely on its Western allies to modernize its ill-equipped armed forces. Recent years have seen unremitting efforts by Manila to modernize its military.

It is within its right that the Philippines strengthens its military to protect its national security. However, amid the simmering South China Sea tensions, this military modernization endeavor could be more than a domestic affair.

The Philippines has continued to erode China's interests in the South China Sea for a long time.

In 1999, the Philippines sent a warship and grounded it on Renai Reef. Intentionally violating its promises to tow it away as soon as possible, Manila shamelessly uses the now rusting ship to claim Renai Reef as part of its territory. It also forcefully drove away Chinese fishermen who were fishing in China's territorial waters.

Given Manila's constant provocations toward China over the South China Sea issue and its obvious intention of beefing up its military presence by embroiling third parties to stir up troubles, we have to question how the Philippines will use the newly acquired military equipment.

Manila claimed the new aircraft will be used to reinforce its capabilities of patrolling in the South China Sea area that it claims as part of its own territory. China needs to draw a red line for such so-called patrol missions.

By no means will Manila's air planes be allowed to fly into China's territorial airspace. It will a pay due price once it crosses the bottom line. Chinese military forces not only are able to effectively detect, trace and intercept any foreign aircraft intruding into our territory, but also have the right to take any necessary measures to safeguard national sovereignty and security.

The Philippines in recent years is busy making waves in the South China Sea for its own interests. The situation would be very different without China exercising restraint. But Manila shouldn't take chances over China's determination to safeguard its sovereignty integrity.