Planning is already underway for three-nation naval patrols in the South China Sea ahead of a high-profile summit next week among the leaders of the United States, Japan and the Philippines, senior officials have said.

Philippine ambassador to the U.S. Jose Manuel Romualdez was quoted by the Financial Times on Wednesday saying that Washington, Tokyo and Manila are finalizing details of an agreement on the patrols, including when to begin and how often they will take place.

The U.S. and the Philippines have conducted joint patrols in the past, but this will be the first time Japan has participated. Both Japan and the Philippines are treaty allies of the United States.

Asked about the plan, Pentagon spokesperson Lieutenant Colonel Martin Meiners told VOA’s Korean Service via email this week that the U.S. has been concerned about “dangerous and destabilizing” actions in the region and is “committed to maintaining deterrence, peace, and stability” with its allies and partners.

Deputy Secretary of State Kurt Campbell said the April 11 summit will be an occasion for “an unprecedented trilateral engagement” among the three countries that will lead to closer cooperation in the South China Sea and elsewhere.

He made the remark Wednesday at an event hosted by the Center for a New American Security in Washington.

A senior U.S. official said the three leaders will discuss what was described as China’s “increasingly risky behavior” in the South China Sea.

“We are increasingly concerned that the PRC’s [People’s Republic of China’s] behavior in this space could lead us closer to really, unintended consequences,” the official said at a background White House press briefing this week.

“U.S. alliances and partnerships are not about China. … But oftentimes, Chinese action motivates a lot — much of what we talk about,” continued the official.

The most recent flare-up came on March 26 when the Chinese Coast Guard used water cannon to prevent a Philippine vessel from conducting a resupply mission to an outpost on a reef in waters within Manila’s 200-mile exclusive economic zone.

White House national security adviser Jake Sullivan told his Philippine counterpart Eduardo Año on Monday that the U.S. supports the Philippines against China’s “dangerous actions on March 26 obstructing a lawful Philippine resupply mission to Second Thomas Shoal.”

Manila claims the shoal in the Spratly Islands as its own territory and has been keeping the BRP Sierra Madre, a World War II-era navy transport ship, grounded on the reef since late 1999.

Patrick Cronin, the Hudson Institute’s Asia-Pacific Security Chair, told VOA via email on Tuesday that the trilateral maritime patrols can provide “both a level of deterrence and a way of blocking Beijing’s efforts to create de facto control over disputed waters and some areas that clearly belong to the Philippines.”

He continued, “China will not desist from its ‘sovereignty enforcement’ efforts, use of white hulls and maritime militia to impose its domestic law on international waters, but it may have to shelve staking further claims in the face of concerted opposition from the three democracies.”

Liu Pengyu, a spokesperson for the Chinese Embassy in Washington, told VOA via email on Wednesday that “the military cooperation between the relevant countries must not interfere in South China Sea disputes,” and called for the three allies to avoid actions that would “harm China’s territorial sovereignty, maritime rights and interests and security interests.”

Liu continued, “The South China Sea issue is a matter between China and some ASEAN countries.”

Among ASEAN member states, the Philippines, Vietnam, Malaysia and Brunei are official claimants against China, whose claims to virtually all of the resource-rich waters have been rejected by an international tribunal.

Prashanth Parameswaran, a fellow at the Wilson Center and founder of the weekly ASEAN Wonk newsletter, told VOA on Tuesday, that “more patrols by more countries is one of many ways to reinforce presence and prevent the nightmare scenario of the South China Sea becoming a Chinese lake.”

He continued, “In addition to alliance networking, the United States and its partners will have to find ways to work with Southeast Asian states which are not formal allies but are nonetheless critical in addressing China’s assertiveness as well.”