U.S. national security advisor Robert O’Brien is visiting Vietnam and the Philippines this month to help bulk up international resistance against Chinese maritime expansion. The U.S. official’s trip following a Vietnam visit last month by Secretary of State Mike Pompeo fortifies the current U.S. position of building up allies from Japan to Australia as a multi-country barrier against Chinese maritime expansion, analysts believe. “Most of us would agree it is a position that has implicitly been mentioned in the past, but now the U.S. government is making it more strongly explicit in support of those claims,” said Dr Collin Koh, maritime security Research Fellow at RSIS.