Nearly 17,000 Filipino and American troops kicked off a three-week joint combat training exercise in the Philippines on Monday that includes maritime drills in the South China Sea where Manila and Beijing have sparred over territorial claims.

France and Australia, which have ramped up defense ties with Manila in the face of China's aggressive behavior in the South China Sea, will join the maritime exercises.

For the first time since the annual Balikatan or "shoulder-to-shoulder" drills started in 1991, the allies will sail outside the 12 nautical miles of the Philippines’ baseline off the western Palawan province, which faces the South China Sea.

The U.S. military’s maiden deployment in the Philippines of a missile system covering a range that could reach China’s southern provinces shows "the drills are beyond self-defense purposes,” according to Cao Weidong, a retired senior researcher at the PLA Naval Research Academy.

The drills, which will run from Monday to May 10, come amid an escalating diplomatic row and maritime encounters between the Philippines and China including the use of water cannon and heated verbal exchanges.

The use of the missile system, according to Philippine military Col. Michael Logico would only be for logistical training and it will not be fired, emphasizing that the drills aren’t aimed against China.

"The intention of targeting China’s mainland is very clear,” Cao said. "We can also deploy corresponding weaponry and alert equipment so that we can respond,” he said without elaborating.

U.S. and Philippine troops will also simulate the sinking of an "enemy ship” and retaking three Philippine islands, seeking to enhance the interoperability of their militaries.

Balikatan will involve "tracking of simulated air threats and targeting them with multiple air and missile defense systems” as well as "integrating multilateral air and land platforms to increase awareness of the maritime security situation,” the U.S. Embassy said in a statement last week.

Officials said the drills are not directed at any external aggressor, but will improve interoperability between their militaries.

"Exercises in those locations operate based on international order and international law and well within your sovereign rights and responsibilities. We're conducting exercises that are normal," U.S. Lt. Gen. William Jurney, Balikatan exercise director, told a briefing.

Beijing's increasing pressure in the South China Sea has alarmed Manila, rival claimants to disputed maritime territory, and other states operating there, including the United States which has reaffirmed its commitment to defend the Philippines against armed aggression in the South China Sea.

China claims most of the South China Sea, which is a conduit for more than $3 trillion of annual ship-borne commerce. Beijing has criticized the joint drills, saying they aggravate tensions and undermine regional stability.

The Permanent Court of Arbitration in the Hague ruled in 2016 that Beijing's expansive claims to the sea had no basis under international law. China rejects the ruling and has built military facilities on disputed atolls to back up its claims.

During joint exercises, U.S. troops and their Manila counterparts will simulate retaking enemy-occupied islands in the northernmost islands of the country close to Taiwan, and in the western Palawan province facing the South China Sea.

The drills will involve around 16,700 troops from both sides, slightly less than last year's 17,600, which were the largest Balikatan exercises since they started in 1991.