A U.S. military attempt to evacuate American citizens from growing violence in Bor, South Sudan, was aborted Saturday after the helicopters took fire, according to the White House.
Four U.S. servicemen were injured in the attempt, but all are in stable condition.
About 500 people are dead and tens of thousands more have been displaced as violence in South Sudan continues into a second week, according the United Nations estimates.
Jen Psaki, a spokeswoman for the State Department, said about 380 U.S. officials and citizens have already been evacuated.
Fighting broke out as a part of a rift ahead of the 2015 elections between former South Sudanese Vice President Riek Machar and President Salva Kiir and appears have spiraled into wider ethnic clashes, according to The Wall Street Journal.
President Barack Obama, who is on vacation in Hawaii, spoke Saturday with top national security officials, including national security adviser Susan Rice, the White House said.
"The president underscored the urgency of helping to support efforts to resolve the differences within South Sudan through dialogue," said a readout of the discussion. "South Sudan's leaders must know that continued violence will endanger the people of South Sudan and the hard-earned progress of independence. Any effort to seize power through the use of military force will result in the end of long-standing support from the United States and the international community."
Obama also sent a message to Congress Sunday, informing them of the attempted evacuation.
"After the aircraft came under fire as they approached Bor, the operation was curtailed due to security considerations and the aircraft and all military personnel on board departed South Sudan without completing the evacuation," he said. "The purpose of this operation was to protect U.S. citizens, personnel and property. As I monitor the situation in South Sudan, I may take further action."
Secretary of State John Kerry spoke to current Sudanese President Kiir late Saturday "to discuss ways to stop the violence in South Sudan."
Kiir told Kerry he was willing to "engage in peaceful dialogue and said he was open to negotiations without preconditions."
Kerry warned about the effect continued violence would have and said he was sending U.S. Special Envoy for Sudan and South Sudan, Ambassador Donald Booth, to help resolve the situation peacefully.
South Sudan voted to become a separate country from Sudan in July 2011.