Speaking before a United Nations conference in Switzerland, Jolie said the situation in the Horn of Africa has moved past the crisis point.
She said drought, famine and war have three quarters of a million people on the brink of starvation.
"How we continue to respond to this period of malnutrition and famine is going to define the work of NGOs, governments and international organizations working in the Horn of Africa," said Jolie. "It will quite starkly determine whether a huge number of people live or die."
U.N. officials said Jolie is hoping to expand her role as an ambassador to better help refugees.