November elections in Myanmar were boycotted by the party led by Suu Kyi, a pro-democracy leader and Nobel Peace Prize winner.
The country's courts refused an appeal by Suu Kyi to have her National League for Democracy party reinstated. The State Department said Suu Kyi received a "veiled threat" on her life if she moves ahead with plans reconstitute her party.
P.J. Crowley, a State Department spokesman, said at his regular press briefing that Washington was concerned about Suu Kyi's safety and security. Myanmar, he said, has a "fundamental responsibility" to make sure she's safe.
"Myanmar needs to recognize the legitimacy of the National League for Democracy, which has struggled for over 22 years to bring democracy to (the) people," he said.
All political prisoners, Crowley said, should be released and the rulers in Myanmar should begin the process of inclusive political dialogue with all opposition groups.
Myanmar said the first general election in more than 20 years would lead to democratic reform, though the international community expressed serious doubts.
Suu Kyi was released for a lengthy house arrest after the election.