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 US, 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 U.S."
Trump was expected to arrive in the Philippines for meetings with leaders of the Association of Southeast Asian Nations (ASEAN) and other East Asian nations, fresh off an Asia-Pacific summit and bilateral visit in Vietnam.
In Hanoi earlier on Sunday, Trump said he was prepared to mediate between claimants to the South China Sea, where four ASEAN countries and Taiwan contest China's sweeping claims to the busy waterway.
"If I can help mediate or arbitrate, please let me know," Trump said at a meeting with Vietnam's president, Tran Dai Quang. "I'm a very good mediator and arbitrator."
In August, foreign ministers of Southeast Asia and China adopted a negotiating framework for a code of conduct in the South China Sea, 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, which 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 nations of ASEAN in Manila on Monday, a diplomat from one of the regional bloc's countries said.
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