The House Foreign Affairs Committee has called for an end to persecution of Myanmar's minority Rohingya Muslims in one of the strongest US congressional criticisms yet of Myanmar's reformist government.
The committee is charged with overseeing US foreign policy, and the resolution, which was passed unanimously on Tuesday, also urged the United States and the wider international community to press Myanmar to protect ethnic and religious minorities.
Myanmar's ambassador to Washington rejected allegations of mistreatment against minorities and said the government would not tolerate incitement to religious hatred.
The prospects of the full House taking up the resolution remain uncertain, but it reflects concern in Congress over the outbreaks of violence in the country as it shifts toward democracy after decades of direct military rule. It also underscores growing congressional scepticism over the Obama administration's engagement policy.
Since mid-2012, close to 280 people, mostly Rohingya, have died in Buddhist-Muslim clashes in western Rakhine state. Some 140,000 Rohingya have been forced into camps, and tens of thousands have fled by boat.
Republican committee chairman Ed Royce said Myanmar could not claim progress on reforms if it did not improve treatment of the stateless Rohingya. He said the US State Department should "take off the rose-coloured glasses".
"We cannot embrace diplomatic reconciliation with the government of Burma while human rights conditions in that country have deteriorated," Royce said.
Myanmar has earned an end to its diplomatic isolation and sanctions relief by undertaking its most significant political and economic reforms in 50 years. Over the past two years, Myanmar has released hundreds of political prisoners and opposition leader Aung San Suu Kyi has been elected to parliament.
There has been bipartisan support for the US administration's engagement of Myanmar, but the goodwill is starting to ebb.
The quasi-civilian government of President Thein Sein faces growing criticism, most recently over its expulsion from Rakhine state of the aid agency Doctors Without Borders.