The P15.5-billion budget for the Association of Southeast Asian Nations (ASEAN) Leaders' Summit should have been given to starving and dying Filipinos across the country, the progressive solon said.
"The South China Sea is better left untouched, nobody can afford to go to war", the Philippines strongman said.
The ASEAN has been pushing for a legally binding code of conduct for all stakeholders in the South China Sea but Beijing has opposed such a framework asserting it will resolve the dispute with respective countries under a bilateral mechanism.
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.
While Duterte's relationship with the USA was strained under the Obama administration, ties have improved since Trump took office earlier this year.
The United States has criticized China's construction of islands and its build-up of military facilities in the sea, and is concerned they could be used to restrict free nautical movement.More news: Goalless draw enough to secure Tunisia World Cup berth
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US President Donald Trump misspells "Philippines" ahead of his trip to the country.
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.
In a joint news conference, Quang said he had "shared my thoughts with (Trump) on the recent developments in this area and it is our policy to settle disputes in the South China Sea through peaceful negotiations, and with respect for diplomatic and legal process in accordance with global law, including the 1982 UN Convention on the Law of the Sea".
In Vietnam on Thursday on the sidelines of an Asia-Pacific economic summit, Duterte boasted that when he was 16 he stabbed to death someone for looking at him the wrong way.
India has been supporting freedom of navigation and access to resources in the South China Sea in accordance with principles of worldwide law, including the 1982 UN Convention on the Law of the Sea.
With China's provocative actions in the South China Sea, Roque said the issue is expected to be discussed by the two leaders.
Others who will be in Manila for the summit meetings include Chinese Premier Li Keqiang, Russian Prime Minister Dmitry Medvedev and leaders from Japan, Canada, South Korea, India, Australia, New Zealand as well as the member states of ASEAN.