People in Peshawar, Pakistan, hold a banner with picture of Burmese democracy leader Aung San Suu Kyi during a protest against violence in Burma on Sept. 7. (Bilawal Arbab/EPA-EFE)

Washington lawmakers who once enthusiastically supported Aung San Suu Kyi's rise to power in Burma have shifted this week to criticism of her silence in the face of a bloody military crackdown on ethnic minorities, the latest sign that the nation's fragile democratic project is on tenuous footing.

Congressional leaders from both parties are adding their voices to the international condemnation of the violence in western Burma that has sent an estimated 164,000 Rohingya Muslims fleeing to Bangladesh and led to growing doubts about Suu Kyi's leadership.

[The Rohingya exodus from Burma is arduous — and sometimes lethal]

On Thursday, a bipartisan group of senators — Democrats Richard J. Durbin (Ill.), Dianne Feinstein (Calif.) and Cory Booker (N.J.), and Republican John McCain (Ariz.) — issued a joint resolution condemning the "horrific acts of violence" against the Rohingya and imploring Suu Kyi "to play an active role in ending this humanitarian tragedy."

Suu Kyi, a longtime democratic icon who plays the role of state counselor to the ruling National League for Democracy, has remained largely silent about the mounting humanitarian crisis. The outcry in Congress reflects the dismay and confusion of the stoic group of Suu Kyi's supporters in Washington that nurtured her throughout her more than 15 years under house arrest and protected her interests as her country emerged from military dictatorship to hold largely democratic elections in November 2015.

Her unwillingness to speak out against the military crackdown, which came in response to insurgent attacks in western Rakhine State, has prompted some former admirers to suggest that Suu Kyi be stripped of the Nobel Peace Prize she was awarded in 1991.

"Part of this is the fault of the international community," said Erin Murphy, a former State Department adviser who accompanied then-Secretary of State Hillary Clinton to the country in 2011. Murphy said she thinks Suu Kyi is being unfairly maligned because supporters had unrealistic expectations.

"We told her story for 25 years, and we don't like who she actually is," Murphy said. "She does not have any idea how to handle this."

[Analysis: Why Aung San Suu Kyi is unlikely to have her Nobel Peace Prize revoked]

The Senate resolution calls on the Burmese government to allow the United Nations "unrestricted access" to assess the situation and provide aid, and to end legal restrictions on citizenship and freedom of movement for the Rohingya. It also calls on Suu Kyi to "live up to her inspiring words" and to "address the historic and brutal repression of the Rohingya."

Other senators, including Benjamin L. Cardin (D-Md.) and Cory Gardner (R-Colo.), have expressed similar concerns this week.

Yet even as U.S. lawmakers sought to exert their influence, one other notable voice has been missing: that of President Trump. Neither the White House nor the State Department has spoken out in recent days, raising concern among Burma supporters that the Trump administration has abdicated the direct intervention that marked the tenure of President Barack Obama.

Obama made Burma, also known as Myanmar, a centerpiece of his administration's foreign policy in Asia, viewing the nation of 53 million as a bulwark against neighboring China's rising influence. Obama made two trips to the country, and last year his administration lifted the remaining economic sanctions, including on the import of jade and rubies.

Trump, by contrast, does not appear to have spoken with Suu Kyi, who skipped a roundtable meeting of Southeast Asian leaders with Secretary of State Rex Tillerson in May because of scheduling conflicts.

"Part of the problem is that there is not the kind of strong interest in the White House as there used to be," said Derek Mitchell, who was U.S. ambassador to Burma from 2012 to 2016.

Trump administration officials did not respond to requests for comment.

Burma's more than 1 million Rohingya Muslims are essentially stateless and have endured decades of discrimination and neglect from the Buddhist majority. The situation worsened in 2012 when more than 100,000 Rohingya were confined to dingy camps, where their movement, access to jobs and education were severely restricted.

The latest exodus of refugees began on Aug. 25 after members of a new insurgent group of Rohingya militants called the Arakan Rohingya Salvation Army attacked dozens of police outposts as well as a military camp, leading to the government crackdown that has left more than 400 dead.

Malaysian Foreign Minister Anifah Aman said that Suu Kyi is "doing nothing," and Turkish President Recep Tayyip Erdoğan said the situation amounts to "genocide."

Pakistani education activist Malala Yousafzai condemned the "tragic and shameful treatment" of the Rohingya, saying she was "still waiting for my fellow Nobel laureate Aung San Suu Kyi to do the same."

On Thursday, Suu Kyi told reporters in Burma that it is "a little unreasonable" to expect her government to have resolved the Rohingya crisis in the 18 months her party has been in power. She emphasized that she is focused on speeding up development and economic opportunities to help alleviate some of the tensions.

Her government also has pledged to implement some of the recommendations on Rakhine state made last month by an advisory commission led by former U.N. secretary-general Kofi Annan.

For Washington, which had invested heavily in Burma's success, the situation is a significant setback. In addition to Obama, Senate Majority Leader Mitch McConnell (R-Ky.) played an instrumental role in supporting Suu Kyi and welcomed her during a visit to Washington last year.

"These latest tragic developments are a troubling sign that the Burmese government and military are moving in the wrong direction," Gardner said in a statement.

Congressional aides said they do not expect renewed economic sanctions on Burma because lawmakers remain wary of taking steps that might set back democratic and economic reforms. Some aides, however, predicted an effort to strip language in the National Defense Authorization Act, which will be voted on this fall, to prompt greater ties between the Pentagon and the Burmese military.

"Congress should suspend any advancement in military relations and make clear that there cannot be further progress while abuses continue," said Rep. Joseph Crowley (D-N.Y.), who has been active on Burma issues.

"There's a lot of distress that she would be willing to jeopardize the international support," Tom Malinowski, who was an assistant secretary of state for democracy and human rights in the Obama administration, said of Suu Kyi. "It seems to me that she has convinced herself that to be a successful politician, she has to give up being a moral icon."

Under the constitution, the Burmese military retains control of 25 percent of the seats in parliament, thus maintaining significant influence. Since the emergence of ARSA, Suu Kyi's government has hardened its position on the Rohingya plight, saying that extremist elements pose a security risk. Last month, the government accusing international aid workers of helping "terrorists" and Suu Kyi has said the Rohingya fighters are burning their own homes.

"We are not going to allow either the security or stability or the integrity of our country to be threatened," Suu Kyi told The Washington Post in a rare interview in October.

During that discussion, she brushed aside criticism over her role: "I've made it very clear that our work is not to condemn but to achieve reconciliation."

Refugees from Burma this week described walking through the jungles for days to reach the border and cross into Bangladesh, where they have built flimsy structures with bamboo and plastic sheeting.

Anisul Mostafa, 40, who fled with his family after the military destroyed his house, said of Suu Kyi: "We thought our distress would be over once she took power. But she is the same, like the others. Perhaps worse."

Gowen reported from Kolkata, India, with reporting from a special correspondent in Teknaf, Bangladesh.