The United States has for the first time described Myanmar's military operation against the Rohingya population as "ethnic cleansing" and is to consider targeted sanctions against those responsible.
Meanwhile, Pope Francis is to meet the head of Myanmar's army as well as Rohingya refugees next week when he visits the troubled country and its hard-pressed neighbour, Bangladesh.
The Vatican spokesperson, Greg Burke, briefed reporters in Rome on the two late additions to the pope's six-day itinerary.
He said that while in Bangladesh, the Pontiff would meet a small number of the estimated half a million mostly Muslim Rohingya who, since August, have fled across the border from Buddhist-dominated Myanmar.
He said that on the Myanmar leg of his trip, Pope Francis will meet the head of the Myanmar army, Senior General Min Aung Hlaing. The venue for tomorrow week's encounter is a church residence in the former capital, Yangon.
The meeting was suggested by Myanmar's Cardinal Charles Maung Bo when he met the pope in the Vatican last Saturday. Mr Burke said both the pontiff and the general had agreed to the proposal.
Cardinal Bo has advised the Pope not to use the word 'Rohingya' while in Myanmar because it is incendiary in the country where they are not recognised as an ethnic group.
Mr Burke said the Pope took the advice seriously but added: "We will find out together during the trip ... it is not a forbidden word"
In September, the United Nations said the army's ongoing actions against the stateless Rohingya in retaliation for dozens of insurgent attacks on security forces on 25 August "seems a textbook example of ethnic cleansing".
Today US Secretary of State, Rex Tillerson went further in a statement on what he termed "horrendous atrocities" against the Rohingya.
"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," he said.
Mr Tillerson avoided using the controversial phrase during his visit last week to Myanmar.
However the latest statement marks a hardening of the US stance on the recent expulsion of some 600,000 stateless Rohingya and the killings of an unknown number of their relatives and friends.
"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 said.
The US supports calls for an independent investigation into what happened in Rakhine state and will pursue actions including possible targeted sanctions, Mr Tillerson said.
"Those responsible for these atrocities must be held accountable," he added.
Pressure had mounted for a tougher US response to the Rohingya crisis before President Donald Trump's maiden visit to Asia this month to attend a summit of Southeast Asian countries, including Myanmar, in Manila.
US government sources said in October that officials were preparing a recommendation for Mr Tillerson that would define the military-led campaign against the Rohingya as ethnic cleansing, which could prompt new sanctions.
Earlier this month, US politicians proposed targeted sanctions and travel restrictions on military officials in Myanmar.
Democratic Senator Jeff Merkley, part of a congressional delegation that visited Rakhine this week, told reporters there yesterday: "This has all the hallmarks of ethnic cleansing."
Myanmar's two-year-old government, led by Nobel laureate Aung San Suu Kyi, has faced heavy international criticism for its response to the crisis, though it has no control over the generals it has to share power with in the country's transition to civilian rule after decades of government by the military.
Myanmar's government has denied most of the claims, and the army last week said its own investigation found no evidence of wrongdoing by troops.
The pope will also meet Ms Suu Kyi in the capital Naypyitaw, on 28 November in an encounter that was already on the schedule.
The Vatican spokesperson also said that a "a small group" of Rohingya refugees will be present at an inter-religious meeting for peace in the Bangladeshi capital, Dhaka on the afternoon of Friday 1 December.
He gave no details of how they would be chosen.