The U.S. envoy to the United Nations met Sudanese refugees fleeing ethnic and sexual violence on Wednesday and said the United States would “do everything in our power to prevent and respond to mass atrocities” in Sudan’s war.

On a visit to the town of Adre in Chad on the border with Sudan, Linda Thomas-Greenfield, a member of President Joe Biden’s cabinet, announced high-profile sanctions targeting the deputy leader of Sudan’s paramilitary Rapid Support Forces (RSF) – and brother of the RSF commander – over human rights abuses.

She met privately with about seven Sudanese women in Adre who told her how they had fled intense violence.

“They all came to Chad out of fear out of what would happen to them next. None of them expressed a sense or even a desire to return home as long as the violence continued,” Thomas-Greenfield told Reuters.

“I felt hopeless because I felt like I couldn’t do anything for them. I couldn’t give them an answer for how the international community could help them,” she said.

Thomas-Greenfield also visited a makeshift hospital run by medical charity Medecins Sans Frontieres (MSF), where some 144 patients were being treated, mainly for malnutrition. As she walked through a ward, a woman was slowly feeding a malnourished baby, while in a nearby bed a sick baby lay on its own.

War broke out in Sudan on April 15 – four years after former President Omar al-Bashir was ousted by a popular uprising. Tensions between the army (SAF) and RSF, which jointly staged a coup in 2021, erupted into fighting over a plan to transition to civilian rule.

“We certainly have reached a level of serious atrocities being committed and it is very reminiscent of what we saw happening in 2004 that led to the genocide determination,” said Thomas-Greenfield before arriving in Chad, referring to Darfur, a region of western Sudan.

“We’re hearing from women who are being brutally gang raped over and over again, villages being raided, there are aerial photos showing mass graves. Signs are there,” she said.

In the early 2000s the U.N. estimates some 300,000 people were killed in Darfur when “Janjaweed” militias – from which the RSF formed – helped the army crush a rebellion by mainly non-Arab groups. Sudanese leaders are wanted by the International Criminal Court for genocide and crimes against humanity.

U.N. aid chief Martin Griffiths warned that Darfur was again “descending into an abyss without mercy or hope.”

“Civilians have been trapped, targeted, raped and murdered. It is unlawful and it is outrageous,” he said in a statement to Reuters.

The United Nations says that since April some 380,000 refugees – mostly women and children – have fled to Chad. Hundreds of thousands more have escaped to Central African Republic, Egypt, Ethiopia and South Sudan.

The U.N. Refugee Agency (UNHCR) has appealed for $1 billion to help provide aid and protection to more than 1.8 million people who are expected to flee Sudan this year. Nearly 7.1 million people are displaced inside the country, according to the International Organization for Migration.

Thomas-Greenfield said the United States would give an additional $163 million in aid and urged others to step up.

The U.N. says half Sudan’s 49 million people need help and has appealed for $2.6 billion – so far, it has secured only 26% of this amount.

“That’s shameful. And I am calling on the international community to do more and give more,” she told reporters in Adre.

Griffiths said that those inside Sudan who had managed to escape the violence now face starvation.

“More than 60 percent of people in West Darfur are highly food insecure, as is over half the population in East and South Darfur,” Griffiths said. “We’re in a race against the clock.”

In recent weeks the United Nations has been able to deliver aid into West Darfur from Chad and has aid trucks ready to reach other parts of the region, but said “unrelenting clashes” were stopping them from reaching the people in need.

“Darfur’s people are caught in a state of near total deprivation. Our message is urgent: Stop the fighting and let us through,” Griffiths said.