"The secretary comes with a series of very specific steps that we'd like to see in terms of the next phase of the process that is under way," the U.S. official said.
"We expect this to be a very thorough review of not only the steps that they have taken, and what we expect to see in the future, but the things that the United States is prepared to do in response."
Potential symbolic moves such as easing travel restrictions on top Myanmar officials or returning a full U.S. ambassador to the country after years of a more junior-level representation could bolster reformers in the government, who are still thought to face some opposition from entrenched military interests.
But Clinton has played down the prospect for any rapid easing of sanctions, most of which would require action by Congress where some lawmakers remain skeptical of the reform effort.
"Secretary Clinton's visit represents a monumental overture to an outlaw regime whose DNA remains fundamentally brutal," Republican Congresswoman Ileana Ros-Lehtinen, the powerful head of the House of Representatives Foreign Affairs Committee, said in a statement. "The enforcement of tough sanctions ... is needed to bring about the needed political change in Burma."
Clinton will travel to the main commercial city of Yangon Thursday and make an offering at the city's imposing Shwedagon Pagoda, whose golden spire has long been a revered symbol of Myanmar's nationhood.
She will also hold two meetings with Suu Kyi, the Nobel peace laureate and democracy advocate who spent 15 of the last 21 years in detention before being released last November. It will be Clinton's first chance to personally compare notes with the pro-democracy heroine, who often draws comparisons with South Africa's Nelson Mandela.
At a private dinner Thursday, and again at a formal meeting at Suu Kyi's home Friday, the two are expected to discuss Suu Kyi's plans to stand in coming by-elections, which would bring her into the formal political process.
Clinton will also meet civil society activists and representatives of ethnic minorities. Conflict between minority guerrillas and the military in border areas may be among the most difficult of Myanmar's political problems to resolve.
In Beijing, Chinese Foreign Ministry spokesman Hong Lei welcomed warmer ties between Myanmar and Western countries.
Asked whether Myanmar's process of opening would undermine China's interests, Hong told a briefing: "We believe that Myanmar and the concerned Western country should strengthen contacts and improve relations on the basis of mutual respect, and we hope that steps like this will help Myanmar's stability and development."