Phnom Penh, Cambodia -- Barack Obama became the first sitting U.S. president to visit Myanmar on Monday, praising the courage of fellow Nobel Peace Prize winner Aung San Suu Kyi while also providing a symbolic nod to initial reforms in a nation once notorious for political repression.
Later Monday, Obama held what an aide called a "tense"meeting with Cambodia's prime minister that emphasized the need for improving human rights in the nation hosting a summit of regional leaders.
Monday's highlight was the several hours Obama spent in Myanmar, the formerly secretive country also known as Burma.
The president met with Suu Kyi at the lakeside villa where she spent years under house arrest for her pro-democracy activism. Obama called the meeting a new chapter between the two countries.
"Here, through so many difficult years, is where she has displayed such unbreakable courage and determination," Obama told reporters, standing next to Suu Kyi. "It is here where she showed that human freedom and human dignity cannot be denied."
Myanmar was politically and economically isolated from the rest of the world for decades until it ended military rule last year.
In a diplomatic show of support, Obama referred to the country by the government's preferred name -- Myanmar -- rather than the colonial name of Burma used by Suu Kyi and democracy activists.
Suu Kyi warned that Myanmar's reform process would be difficult.
"The most difficult time in any transition is when we think success is in sight, then we have to be very careful that we are not lured by a mirage of success, and that we are working toward its genuine success for our people and friendship between our two countries," she said.
Before meeting Suu Kyi, Obama spent an hour with Myanmar President Thein Sein, whose reform drive has seen the release of hundreds of political prisoners and steps to open the country's economy.
The democratic and economic reforms started by the president could lead to "incredible development opportunities," Obama said.
Thein Sein, who wore a long purple sarong and white shirt, told Obama he was committed to strengthening bilateral relations.
The name Myanmar was introduced by the former military regime 23 years ago and is preferred by the country's current leaders. But until Monday, the Obama administration had largely stuck to the British colonial name of Burma.
As well as meeting Thein Sein and Suu Kyi, Obama delivered a speech at the University of Yangon in which he urged the country to continue its "remarkable journey."
"The flickers of progress that we have seen must not be extinguished," Obama said. "Reforms launched from the top of society must meet the aspirations of citizens who form its foundation."
After leaving Myanmar, Obama traveled to Cambodia for a summit of the Association of Southeast Asian Nations that began with a first round of talks and a dinner on Monday night.
The president also discussed human rights issues in the host country with Prime Minister Hun Sen, highlighting the case of a Cambodian radio broadcaster sentenced to prison for something he said on air about land seizures, according to Deputy National Security Adviser Ben Rhodes.
Rhodes described the meeting as "tense," in keeping with past U.S. efforts to raise human rights issues with Cambodia.