The United States, Japan and the Philippines have staged joint naval drills to boost crisis readiness off a disputed South China Sea shoal as a Chinese military ship kept watch from a distance.

Two Philippine officials say that American and Filipino security officials have agreed to keep a U.S. mid-range missile system in the northern Philippines indefinitely to boost deterrance despite China’s expressions of alarm.

A U.S. admiral says American forces are ready with a “range of options” to deal with increasing acts of aggression in the disputed South China Sea after consultations with treaty ally the Philippines.

Indo-Pacific commander Adm. Samuel Paparo says the U.S. military is open to the possibility of escorting Philippine ships in the disputed South China Sea, depending on consultations under the allies’ 1951 Mutual Defense Treaty.

Officials say a Philippine fisheries bureau plane has been threatened by flares fired from a Chinese island.

The Philippine military chief has demanded China return several rifles and equipment seized by the Chinese coast guard in a disputed shoal and pay for damage in an assault he likened to an act of piracy in the South China Sea.

American and Filipino forces have launched their largest combat exercises in years in a show of allied firepower that will include joint sails with the French navy and a ship-sinking drill near the disputed South China Sea that has alarmed Beijing.

President Ferdinand Marcos Jr. has defended his decision to allow a larger United States military presence in the country as vital to territorial defense.