UNHCR commissioner Ruud Lubbers praised her "compassion"

Jolie, who returned from a visit to Pakistan on Sunday, was emotional as she described her meeting with Afghan refugees there.

"It's still very hard to talk about it," she said after the Geneva ceremony in which she was formally appointed UNHCR ambassador.

"It is the worst situation I think, because there is no end in sight for the needs of these people."

High Commissioner Ruud Lubbers said he believed Jolie would be able to bring the issue of refugees to the attention of young people.

"We look after 22 million people, and that is hardly known by young people," he said.

Angelina Jolie films

Hackers (1995) Playing God (1997) Gia (1998) Pushing Tin (1999) The Bone Collector (1999) Girl, Interrupted (1999) Gone in 60 Seconds (2000) Tomb Raider (2001)

"She can show her personal commitment as a young person to convince the younger generation that something has to be done here."

The 26-year-old actress has been paying discreet visits to a number of countries on behalf of the UNHCR, including one to Cambodia where scenes from Tomb Raider were shot.

She has released diaries she kept during visits to Sierra Leone and Tanzania on the internet to publicise the work of the UNHCR.

Jolie says she plans to address the US congress on issues relating to refugees, but also hopes to get her message across to ordinary American citizens about the United Nations.

Jolie was the number one choice to star in Tomb Raider

"People need to understand that all of them, if they had a chance, would like to go home," she said.

"They are saving their lives and trying to survive and keep their families alive."

Jolie is best known for her Oscar-winning role as the unhinged Lisa in Girl, Interrupted and for parts as a car thief in Gone in 60 Seconds and a policewoman hunting a serial killer in The Bone Collector.

Other notable roles include a tomboy computer crook in Hackers in 1995.

She is married to actor Billy Bob Thornton.

Jolie takes over the goodwill ambassador role from US opera singer Barbara Hendricks, who remains an honorary ambassador.

Former ambassadors have included actress Sophia Loren and actor Richard Burton.