U.N. special envoy Angelina Jolie urged world powers today to do more to help the millions who have fled the conflict from Syria's 5-year-long civil war, as she visited refugees in Lebanon's Bekaa Valley.

The war has killed 250,000 people, displaced half of Syria's population and created Europe's worst refugee crisis since World War Two. Talks on a political solution are underway in Geneva, but hopes of progress are modest.

As a diplomatic solution eludes politicians, simply coping with the growing humanitarian crisis is not a viable alternative, Jolie said.

"We need governments around the world to show leadership, to analyze the situation and understand exactly what their country can do, how many refugees they can assist and how," she said at a muddy camp in Saadnayel, about 15 km (10 miles) from the Syrian border.

Turkey, Jordan and Lebanon host the vast majority of the 4.8 million refugees created by the conflict. The one million registered refugees in Lebanon represent a quarter of the country's population.