MANILA - Riot police used water canon to prevent hundreds of protesters reaching the U.S. embassy in Manila on Sunday, just a few hours before the arrival of President Donald Trump in the Philippines for a regional summit and the last leg of his Asia tour.Carrying placards declaring "Dump Trump" and "Down with US 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 US."Trump was expected to arrive in the Philippines at around 5 p.m. 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."The Philippines will be Trump's last stop on a marathon tour that has taken him to Japan, South Korea, China as well as Vietnam.