Manila. The United States, Japan and Australia are planning a joint navy drill in the South China Sea off the western Philippines this week to underscore their commitment to the rule of law in the region after a recent show of Chinese aggression in the disputed waters, Filipino security officials said Sunday.

On Aug. 5, Chinese coast guard ships used water cannons against Philippine vessels in the contested waterway where disputes have long been regarded as a potential flashpoint and have become a fault line in the rivalry between the US and China in the region.

The drill will include three aircraft and helicopter carriers sailing together in a show of force and undertaking joint drills. Their commanders are set to meet with Filipino counterparts in Manila after the offshore drills, two Philippine security officials told The Associated Press.

Both spoke on condition of anonymity because they are not allowed to publicly discuss details of the planned drills.

The US plans to deploy an aircraft carrier, the USS America, while Japan would send one of its biggest warships, the helicopter carrier JS Izumo. The Royal Australian Navy would send its HMAS Canberra, which also carries helicopters, one of the two officials said, adding that the joint drill was planned a few months ago.

The Philippines would not be part of this week's drills due to military logistical limitations but is open to becoming a participant in the future, the official said.

The United States, Japan and Australia were among several countries that immediately expressed support for the Philippines and concern over the Chinese action following the tense stand-off earlier this month.

Philippine officials said six Chinese coast guard ships and two militia vessels blocked two Philippine navy-chartered civilian boats taking supplies to the Philippine forces stationed at the Second Thomas Shoal. One supply boat was hit with a powerful water cannon by the Chinese coast guard while the other managed to deliver food, water, fuel and other supplies to the Filipino forces guarding the shoal, the Philippine military said.

The Chinese coast guard acknowledged its ships used water cannons against the Philippine vessels, which it said strayed without permission into the shoal, which Beijing calls Ren’ai Jiao.

“In order to avoid direct blocking and collisions when repeated warnings were ineffective, water cannons were used as a warning. The on-site operation was professional and restrained, which is beyond reproach,” the Chinese coast guard said. “China will continue to take necessary measures to firmly safeguard its territorial sovereignty.”

The Philippine military said on Saturday that it would again attempt to deliver basic supplies to its forces in the Second Thomas Shoal, but didn't provide further details.

The mission “to the shoal is a clear demonstration of our resolve to stand up against threats and coercion and our commitment in upholding the rule of law,” the Armed Forces of the Philippines said in a statement.

Following the incident, Washington renewed a warning that it is obliged to defend its longtime treaty ally if Philippine public vessels and forces come under armed attack, including in the South China Sea.