International donors at a conference in Oslo, Norway, have pledged $600 million for South Sudan, where the United Nations says 4 million people are at risk of starvation.
 
Tuesday's pledges are in addition to the $536 million already promised. Norwegian Foreign Minister Boerge Brende calls the pledges significant and says they will save lives.
 
But U.N. officials say the pledges still are short of the $1.8 billion needed for South Sudan.
 
Fighting between government forces and rebels is causing a huge refugee problem and preventing farmers from planting crops ahead of the rainy season.
 
The United States was the largest single donor at the conference - pledging $300 million.
 
South Sudan's Foreign Minister Barnaba Marial Benjamin said the government will guarantee free movement of humanitarian aid, including in rebel-held areas.

Some information for this report comes from AFP and Reuters.