Kerry, a practicing Catholic whose experiences during the Vietnam War inspired his political activism, visited the French-colonial era Notre Dame Cathedral in southern Ho Chi Minh City as he began his first official visit to the nation as the top US diplomat.
Washington is eager to underscore its commitment to Asia after its "pivot" policy was shaken earlier this year when the US government shutdown forced President Barak Obama to cancel a trip to the region, allowing China to occupy centre stage at key regional summits.