US President Barack Obama is making a historic visit to Burma, the first by a sitting US president.
Crowds of people, some waving US flags, lined the streets of Rangoon as he drove to meet President Thein Sein.
He said his goal was to "sustain the momentum for democratisation", pledging stronger ties if reforms continued.
Critics warn the visit could be too early in the reform process, but on Monday reports suggested several dozen political prisoners were to be freed.
Mr Obama's visit is intended to show support for the reforms put in place by Thein Sein's government since the end of military rule in November 2010.
Activists have cautioned that political prisoners remain behind bars and ethnic conflicts in border areas are unresolved.
A prisoner amnesty last week is not thought to have included any of the 280-330 political detainees that rights groups say are imprisoned. But another amnesty was subsequently announced, with about two-thirds of the 66 prisoners to be freed reportedly political detainees.
Mr Obama touched down in Rangoon in Air Force One on Monday morning after a short flight from Thailand. He is spending some six hours in the country but will not visit the capital, Nay Pyi Taw.
Instead his time is being spent in Burma's commercial capital where, as well as meeting top leaders, he will also address students at a university at the heart of pro-democracy protests in 1988 that were violently suppressed by the regime.
Mr Obama is also expected to announce an aid pledge worth $170m (£107m).
Addressing journalists after his meeting with Thein Sein, Mr Obama said he recognised that the country was taking "just the first steps on what will be a very long journey".
"But we think a process of democratic and economic reform here in Myanmar [Burma] that has been begun by the president is one that can lead to incredible development opportunities," he said.
Thein Sein said the two sides had reached agreements "for development of democracy in Myanmar and for promoting of human rights to be of international standard". The two sides would continue to work together to develop education and healthcare services, he said.
Mr Obama went on from that meeting to talks with Ms Suu Kyi at the lakeside home where she spent many years under house arrest.
The pro-democracy leader thanked the US for its support but warned that difficult times could lie ahead.
"I say difficult because the most difficult time in any transition is when we think that success is in sight," she said.
"Then, we have to be very careful that we are not lured by a mirage of success and that we are working towards genuine success for our people."
The US president and his team also made a brief stop at Shwedagon Pagoda, the Rangoon landmark that has been at the heart of many key moments in the country's history.
Mr Obama is being accompanied by US Secretary of State Hillary Clinton - who returns to Burma almost a year after her first visit.
Thein Sein's government came to power after widely-criticised polls in November 2010 that saw military rule replaced with a military-backed civilian government.
Since then - to the surprise of many - his administration has embarked on a reform process. Many - but not all - political prisoners have been freed, censorship has been relaxed and some economic reforms enacted.
Ms Suu Kyi was freed from house arrest shortly after the polls. Her NLD party, which boycotted the elections, has since rejoined the political process. It now has a small presence in parliament, after a landslide win in by-elections deemed generally free and fair in April.
In response, many Western nations have relaxed sanctions against Burma and begun a process of engagement.
But rights groups have cautioned against a rush to embrace the South East Asian nation, warning that political prisoners remain behind bars and ethnic conflicts are unresolved.
In recent months, bitter communal violence between Muslims and Buddhists in Rakhine state has left more than 100,000 people - mostly Muslim Rohingyas - displaced.
Mr Obama has stressed that his visit is not an unqualified endorsement of the Burmese government.
"I don't think anybody is under any illusion that Burma's arrived, that they're where they need to be," he said in Bangkok on Sunday.
"On the other hand, if we waited to engage until they had achieved a perfect democracy, my suspicion is we'd be waiting an awful long time," he added.
After visiting Burma, Mr Obama will head to Cambodia to join a meeting of the Association of South East Asian Nations, in a trip that underlines the shift in US foreign policy focus to the Asia-Pacific region.
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