Coinciding with the president's visit, the government of Myanmar announced further human rights steps to review prisoner cases and de-escalate conflicts in ethnic regions of the country.
But Obama urged even more, calling for a government where, as he put it, "those in power must accept constraints."
"The flickers of progress that we have seen must not be extinguished," Obama said in an address televised to the nation.
Rhodes said the president was moved by the throngs of people who lined the streets to greet him during the visit. The president made one unscheduled stop at the Shwedagon Pagoda. After seeing the pagoda as Air Force One approached Yangon, then seeing the outpouring of support from the citizens for whom the site means so much, Obama personally decided to make the unscheduled stop, Rhodes said.
As Obama arrived in Cambodia, he was dogged by concerns from human rights groups that have cast Hun Sen as a violent authoritarian and have voiced apprehension that Obama's visit will be perceived within Cambodia as validation of the prime minister's regime. But administration officials say Obama, when he meets with Hun Sen on Monday, will raise concerns about the government's human rights record.
Still, many Cambodians credit Hun Sen with helping the country emerge from the horrors of the 1970s Khmer Rouge reign, when systematic genocide left 1.7 million dead. Vietnam invaded and ousted that regime in 1979. By 1985, Hun Sen had become prime minister.
Kuhnhenn reported from Yangon, Myanmar.
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