The officials are also expected to travel to Yangon on Wednesday to meet Aung San Suu Kyi, the opposition leader, according to the US embassy in Yangon.
Nyan Win, a spokesman for Aung San Suu Kyi's National League for Democracy (NLD), told the AFP news agency that the party sees the visit "as the start of direct engagement between the US and Myanmar government".
|Campbell, left, and Marciel are the most senior US officials to visit since 1995 [AFP]
"But we do not expect the exact and big change from this meeting. This visit is just a first stage," he added.
He said the NLD had been told that the US envoys would meet the party's central executive committee at their headquarters on Wednesday and would meet Aung San Suu Kyi the same day.
Washington signalled a sharp shift in its policy towards Myanmar in September, saying it would be "engaging directly with Burmese authorities", and holding the highest-level contact in a decade with Myanmar officials in New York later in the month.
But the US has also said that it will not ease sanctions on the Southeast Asian country without progress on democracy and human rights.
Larry Dinger, the charge d'affaires at the US embassy in Yangon, said in an interview published in the semi-official Myanmar Times newspaper this week that Washington wanted to make progress on "important issues" but would maintain sanctions "until concrete progress is made".
Aung San Suu Kyi has welcomed US engagement of the military government and in late September wrote a letter to Than Shwe to offer her co-operation in getting Western sanctions lifted after years of backing harsh measures against the ruling generals.
The generals granted the Nobel peace laureate two rare meetings with a government minister and allowed her to see Western diplomats last month.
Thein Sein, Myanmar's prime minister, told Asian leaders at a summit in Thailand last month that the government sees a role for Aung San Suu Kyi in fostering reconciliation ahead of the promised elections next year, but it was not clear what form this would take.
Aung San Suu Kyi, who has spent 14 of the past 20 years in detention, continues to be kept under house arrest after having her detention extended by 18 months in August over an incident in which an American man swam to her lakeside house uninvited.
A foreign diplomat in Yangon told the AFP that the visit by the US envoys was "important but at the same time without immediate consequence".
"It is necessary to be cautious. Everyone knows there is a risk of relations going cold again in two months," the diplomat said.