The United States has declared the ongoing violence against the Rohingya population "ethnic cleansing" and threatened to impose sanctions against those behind "horrendous atrocities" in Myanmar.
Donald Trump's Secretary of State Rex Tillerson issued a statement using the terminology which was previously avoided when he visited the country last week.
He said: "After a careful and thorough analysis of available facts, it is clear that the situation in northern Rakhine state constitutes ethnic cleansing against the Rohingya."
The politician said America would "pursue accountability through US law, including possible targeted sanctions" against those responsible for the alleged abuses, which has seen hundreds of thousands of Rohingya fleeing to neighbouring Bangladesh.
The shift in stance comes as it aims to raise pressure on Myanmar's military and civilian leaders after human rights groups accused the military of atrocities.
Alleged atrocities include mass rape during so-called clearance operations – part of a brutal crackdown after Rohingya insurgents attacked Myanmar security forces in August.
More than 600,000 Rohingya Muslims have since fled Myannmar, a majority Buddhist state.
Mr Tillerson said: "These abuses by some among the Burmese military, security forces, and local vigilantes have caused tremendous suffering and forced hundreds of thousands of men, women, and children to flee their homes in Burma to seek refuge in Bangladesh."
He condemned the insurgent attacks but added: "No provocation can justify the horrendous atrocities that have ensued."
Aung San Suu Kyi, the leader of Myanmar's government and Nobel Peace Prize winner, has come under fire for her response to the crisis, although she has no power over the generals her government shares power with.
A senior US official told reporters: "It's not a situation that is completely under her authority, but certainly we are counting on her to show leadership and also to work through the civilian government with the military to address the crisis."
Another official said the US was looking into whether the crisis constituted genocide or crimes against humanity, which would violate international law.