The United States' top official for foreign aid issued a firm and emotional warning to Myanmar on Thursday about the lack of progress over how it treats Rohingyas and other ethnic minority groups, reports ABC News.

Two years after violent attacks by Myanmar security forces and local militias against the Muslim ethnic minority killed thousands and sent more than 750,000 across the border as refugees, little has changed on the ground in Myanmar's northwest Rakhine state.

Critics say it's because the US, the United Nations and others have not done enough to pressure the government.

"They're not on the right path and a democratic journey, and I worry a great deal," Mark Green, administrator of the US Agency for International Development, told the ABC News in an interview.

Myanmar, sometimes still known by its former name Burma, has been accused of genocide by the UN, which issued a detailed report last year on the campaign to kill, rape, and torture Rohingya, drive them from their homes, and destroy their towns and villages.

US Secretary of State Mike Pompeo issued a similar report by American investigators with damning, graphic details in September 2018, but the US stopped short of calling it genocide and instead labeled it ethnic cleansing.

Myanmar denies it has carried out a genocide, instead saying the attacks against Rohingya were about countering terrorism.

In the last year, it has negotiated with neighboring Bangladesh to begin returning back across the border some of the nearly 1 million Rohingya refugees living in squalid conditions. But nearly none have volunteered to go, with conditions in Myanmar still dangerous and the government refusing to guarantee protections, a return to their land, or even citizenship.

A UN-appointed investigative team reported last week that the same violent conditions exist.

"There is a strong inference of genocidal intent on the part of [Myanmar's government], there is a serious risk that genocidal actions may recur, and Myanmar is failing in its obligation to prevent genocide, to investigate genocide and to enact effective legislation criminalizing and punishing genocide," the report found.

With enormous strain on its poor local communities, Bangladesh announced Thursday it will begin to build barbed-wired fences around Rohingya refugee camps to stop their expansion, according to the Associated Press. There are also growing concerns about unrest in the camps and the potential for refugees to be radicalized or turn to criminal activity.

"I'm painfully aware" of Myanmar's lack of progress, said Green, a former US ambassador to Tanzania and Republican congressman. "It is less than satisfactory," he added.

During this year's UN General Assembly, however, there was little focus on the issue, and the UN Security Council has never voted on a resolution on the August 2017 violence.

"They have stopped the democratic journey," said Green. "It is not continuing as long as you have Rohingya and others who are denied their most basic rights, and so we need to be firm in that message all the time, and consistent."

The messages from Pompeo and the US have been "firm and clear," he argued, but many US officials are afraid of pushing too hard and provoking a backlash against civilian rule or driving Myanmar into China's orbit.

To that end, Assistant Secretary of State for Economic and Business Affairs Manisha Singh traveled to Myanmar in August to promote economic exchange, but her visit came just days after the UN-appointed investigative team reported that the military has deep business ties, which "substantially enhances its ability to carry out gross violations of human rights with impunity." Before the trip, human rights groups wrote Singh a letter expressing alarm that US investment could "support, directly or otherwise, the military, or exacerbate conflict, and undermine efforts to promote accountability and conditions for the safe, dignified and voluntary return of displaced persons."