UN is 'stretched' in South Sudan says US ambassador
20 December 2013 Last updated at 12:39 GMT
The US ambassador to South Sudan, Susan Page, has said the UN mission in the country is "stretched".
Her comments came after President Obama urged political leaders in South Sudan to restore calm and work urgently for reconciliation.
Hundreds of people have died in the last few days after clashes in the capital Juba spread around the country.
President Salva Kiir has accused his ex-deputy Riek Machar of trying to carry out a coup.
An estimated 34,000 people have taken refuge at United Nations compounds.
Three Indian peacekeepers were killed on Thursday when a UN base sheltering refugees came under attack near South Sudan's eastern border with Ethiopia.