ABC News' Mary Bruce, Reena Ninan, Ann Compton and Jon Garcia report:
YANGON, Myanmar - Becoming the first sitting U.S. president to visit this long-isolated nation, President Obama today will "extend the hand of friendship" as the country emerges from five decades of harsh authoritarian rule, but caution that the young democracy has "much further to go."
"Instead of being repressed, the right of people to assemble together must now be fully respected," the president will say in his address at the University of Yangon, according to excerpts released by the White House. "Instead of being stifled, the veil of media censorship must continue to be lifted. As you take these steps, you can draw on your progress."
Showcasing one of the foreign policy accomplishments of his first term, Obama will praise the "dramatic transition" that Myanmar has made as he attempts to "lock-in" the nation's reforms and encourage additional progress.
Obama made history when Air Force One touched down at 9:35 am local time. He was greeted by tens of thousands of people lining the streets of Yangon, including roughly 2,000 school children who stood shoulder-to-shoulder on this muggy day in crisp white shirts and traditional green longyis waving U.S. and Myanmar flags.
Obama's first stop was at the government headquarters, where he met with reformist President Thein Sein.
"I've shared with him the fact that I recognize this is just the first step on what will be a long journey," Obama told reporters, with Sein at his side. "But we think a process of democratic and economic reform here in Myanmar that has been begun by the president is one that can lead to incredible development opportunities."
While the U.S. uses the term "Burma," the former name of the country, Obama referred to it as "Myanmar," the preferred terminology of the former military government when meeting with Sein.
"I shared with President Thein Sein our belief that the process of reform that he has taken is one that will move this… country forward."
The president then made a personal visit to the home of opposition leader, and fellow Nobel laureate, Aung San Suu Kyi, where she lived under house arrest before being released two years ago.
As the president's motorcade pulled up to the large stucco home along a lake, throngs of onlookers outside the gate chanted "Obama! Obama!"
The petite Suu Kyi walked to the limousine and she and Obama greeted each other with their hands making the traditional sign of prayer and a nod of the head. Then, a handshake. Suu Kyi turned back to the car looking for Clinton. The two women embraced eagerly with big smiles all around before all three headed inside to catch up.
"I'm proud to be the first American president to visit this spectacular country," the president told reporters after their visit. "One of my first stops is to visit with an icon of democracy, who has inspired so many people, not just in this country but all around the world. Here through so many difficult years is where she displayed such unbreakable courage. It's here where she showed human freedom and dignity cannot be denied."
"I have come to keep my promise, and extend the hand of friendship," Obama will say in his speech culminating the visit. "America now has an Ambassador in Rangoon, sanctions have been eased, and we will help rebuild an economy that can offer opportunity for its people, and serve as an engine of growth for the world."
Obama will warn that "reforms launched from the top of society must meet the aspirations of citizens who form its foundation."
"The flickers of progress that we have seen must not be extinguished - they must become a shining North Star for all this nation's people," he will say.
Obama's visit, a brief six-hour stop on his whirlwind tour of Southeast Asia, is seen as a symbolic validation of the country's changes. Human rights groups, however, have said the president's trip is premature because the government continues to hold political prisoners and human rights abuses are ongoing.
In his remarks, the president will note that to protect freedom, those in power must accept constraints. "That is how you must reach for the future you deserve - a future where a single prisoner of conscience is one too many, and the law is stronger than any leader; where no child is made to be a soldier, and no woman is exploited; where national security is strengthened by a military that serves under civilians, and a Constitution guarantees that only those who are elected by the people may govern," he will say.
"On that journey, America will support you every step of the way: by using our assistance to empower civil society; by engaging your military to promote professionalism and human rights; and by partnership with you as you connect your progress towards democracy with economic development."
This journey to Myanmar is a first, but also a poignant last for Secretary of State Hillary Clinton. In Yangon, she came down the air-stairs alongside President Obama for what the White House calls her final trip with him as Secretary of State, her final official ride on Air force One as the architect of his foreign policy. Clinton has said she will not remain for a second term.