Two senior US envoys have held separate talks with Burmese Prime Minister Thein Sein and detained pro-democracy leader Aung San Suu Kyi.
The visit of US Assistant Secretary of State Kurt Campbell and his deputy is the highest level contact between the two governments for more than a decade.
Mr Campbell met the prime minister in the capital, Naypyitaw, before flying to Rangoon to meet Ms Suu Kyi.
No details of either set of talks have been released.
The visit comes weeks after the US announced it would engage with Burma's military junta in an attempt to promote reform.
But the US envoys are not meeting Burma's top leader, General Than Shwe.
Aung San Suu Kyi said nothing as she entered the lakeside hotel in Rangoon to meet the US officials.
But the fact that she was seen in public and was allowed to meet such a high-level US delegation is being seen as positive, reports BBC South East Asia correspondent Rachel Harvey.
After the talks, which lasted two hours, Mr Campbell was expected to meet with leaders of Ms Suu Kyi's National League for Democracy (NLD), officials said.
The US diplomats earlier met Burmese Prime Minister Thein Sein in Naypyidaw. Details of those discussions have not been made public.
The visit is the latest evidence of Washington's new approach towards Burma, our correspondent says, a policy described as engagement alongside sanctions.
There is a growing belief in diplomatic circles that isolating the military leadership has not had the desired effect. The question now is whether face-to-face dialogue is any more productive, our reporter adds.
Burma's military junta says multi-party elections will take place in early 2010 - the first polls in almost two decades.
Ms Suu Kyi's NLD won the last elections, in 1990, but was never allowed to take power.