US President Donald Trump landed in the Philippines on Sunday for a summit of Southeast and East Asian nations, hours after offering to mediate on competing claims to the South China Sea that have long stoked tensions in the region.
It will be the last leg of a marathon Asia tour that, despite Trump's "America First" policy, may reassure some that his administration remains committed to a region that Beijing sees as its strategic domain.
In Vietnam earlier on Sunday, Trump said he was prepared to mediate in the dispute over the South China Sea, where four Southeast Asian countries and Taiwan contest China's sweeping claims to the busy waterway.
But Philippines President Rodrigo Duterte, host of two days of summit meetings that will bring together Southeast Asian and East Asian nations, said the thorny issue was better left untouched. All the claimants will be at the summit, except for Taiwan.
"We have to be friends, the other hotheads would like us to confront China and the rest of the world on so many issues," Duterte said at a pre-summit business conference in Manila.
"The South China Sea is better left untouched, nobody can afford to go to war. It can ill-afford a violent confrontation."
The United States and its former colony, the Philippines, have been strategic allies since World War Two.
Trump is expected to try during the summit to shore up relations, which have been strained by the mercurial Duterte's notorious anti-U.S. sentiment and his enthusiasm for better ties with Russia and China.
Police used water canon to prevent hundreds of protesters reaching the U.S. embassy in Manila ahead of Trump's arrival.
Carrying placards declaring "Dump Trump" and "Down with U.S. Imperialism," the left-wing protesters were blocked by police in riot gear with shields and batons, and then showered with jets of water from a fire engine.
"Trump is the CEO of the imperialist government of the U.S., said 18-year-old student Alexis Danday after the protesters were scattered. "We know he is here to push for unfair treaties between the Philippines and the US"
On a tour that has taken him to Japan, South Korea, China and Vietnam, Trump and his team have repeatedly used the term "Indo-Pacific" instead of "Asia-Pacific" for the region, which some see as an effort to depict it as more than China-dominated.
Pacific Rim nation leaders agreed in Vietnam on Saturday to address "unfair trade practices" and "market distorting subsidies," a statement that bore the imprint of Trump's efforts to reshape the global trade landscape.
The summit of Asia-Pacific Economic Cooperation (APEC) countries in Vietnam put on show the contrasting vision of the "America First" policy with the traditional consensus favouring multinational deals that China now seeks to champion.
Leaders at the Philippines summit will discuss the South China Sea, but mainly to agree on a procedural step to cool tensions.
In August, foreign ministers of Southeast Asia and China adopted a negotiating framework for a code of conduct in the resource-rich waterway, a move they hailed as progress but one seen by critics as a tactic to buy China time to consolidate its power.
The framework seeks to advance a 2002 Declaration of Conduct (DOC) of Parties in the South China Sea. The DOC has mostly been ignored by claimant states, particularly China, which has built seven man-made islands in disputed waters, three of them equipped with runways, surface-to-air missiles and radars.
The framework will be endorsed by China and the 10-member Association of Southeast Asian Nations (ASEAN) on Monday, a diplomat from one of the regional bloc's countries said.