Angelina Jolie will be taking on a new role in the world's most acute refugee crises, the American actress and United Nations refugee agency UNHCR said on Tuesday.

UNHCR sources told Reuters they expected her to be named Special Representative on the Afghan refugee situation, to help resolve the fate of 2.7 million Afghan refugees in Pakistan and Iran. But a representative for the actress said there was no final agreement.

Jolie, who has served for 10 years as goodwill ambassador for the U.N. High Commissioner for Refugees, and donated $5 million to its aid operations, declined to be specific, telling reporters:

Antonio Guterres, U.N. High Commissioner for Refugees, said Jolie would become "our special envoy mainly for the most dramatic refugee situations that require a lot of advocacy" and help mobilize strong international support.

"We will be asking you to do more and more in this regard," he said.

The UNHCR later issued a statement saying that her expanded role had not yet been finalized. "A number of countries are under consideration and discussions are ongoing with relevant authorities regarding Ms. Jolie's additional role," it said.

The U.S.-based Endeavor Group, which represents Jolie, told Reuters: "There is no agreement. Nothing is final."

The Oscar-winning Jolie said refugees whom she had met during her 40 field missions for UNHCR in hotspots from Pakistan to Kenya were "among the most vulnerable and yet the most resilient people in the world."

Jolie, who makes her directorial debut with the Bosnian wartime romance film "In the Land of Blood and Honey," due to be released in December, has six children.

On recent UNHCR missions to Malta and Tunisia, she met families who had fled their native Somalia only to be uprooted again by fresh conflict in Libya, she said.

During a visit in March to the Afghan village of Qala Gadu, north of Kabul, where girls' schools and teachers remain targets of violence, a girl named Sahira pledged to complete her studies through to the age of 18 if the actress helped build a school.

The September 20 killing of Burhanuddin Rabbani, Kabul's chief peace negotiator, derailed efforts to forge dialogue with the Taliban to end the 10-year war and raised fears of a widening of Afghanistan's ethnic rifts.

Although millions of Afghans have returned home in the past decade, Pakistan and Iran still host 1.7 million and 1 million Afghan refugees, respectively, according to the agency.

Jolie made a surprise appearance on Monday night at the UNHCR's ceremony to honor a Yemeni aid group credited with rescuing thousands of Somali refugees who arrive in Yemen each year.

Miami-based Colombian pop icon Juanes performed his hits "It's Time to Change" and "Camisa Negra" (The Black Shirt). Norway's Sivert Hoyem, vocalist of the rock band Madrugada, sang "Prisoner of the Road," a ballad about fleeing violence.