US sending Marines to Africa in preparation for evacuations in South Sudan

Dec. 18, 2013: In this photo released by the U.S. Air Force, soldiers of the East Africa Response Force (EARF), a Djibouti-based joint team assigned to Combined Joint Task Force-Horn of Africa, depart from a U.S. Air Force C-130 Hercules in Juba, South Sudan to support with an ordered departure of personnel from the city. (AP/U.S. Air Force)

The U.S. military is sending Marines and aircraft to the Horn of Africa in anticipation they may be needed to respond to the violence in South Sudan, Fox News confirms.

A senior U.S. Defense official told Fox News that 150 Marines are being moved from Moron, Spain, to Camp Lemonnier in Djibouti, in case the State Department asks for their assistance in evacuating U.S. citizens left in South Sudan. So far, no request from the department has yet come in to evacuate the roughly 100 U.S. citizens left in the country.

The decision comes after four U.S. troops were injured Saturday when gunfire hit evacuation aircraft. Three of those troops are stable and being sent to the military hospital in Germany, a spokesman said, while the fourth continues to get treatment in Nairobi, in neighboring Kenya.

Forty-five U.S. troops already are in South Sudan providing security. Others are in Djibouti, where the U.S. maintains its only permanent military base in Africa. Ten aircraft are now stationed there including Osprey helicopters and C-130 transport planes.

The U.S. continued intense diplomatic efforts Monday to calm the roiling ethnic violence, including holding a meeting between the U.S. special envoy for South Sudan, Donald Booth, and South Sudan President Salva Kiir.

Troops deployed last week helped evacuate Americans and other foreign nationals and provided security at the U.S. Embassy in Juba.

Toby Lanzer, the U.N.'s humanitarian coordinator, said Australians, Ugandans and Ethiopians are also among 15,000 total people seeking protection at a U.N. base in Bor, a city that could see increasing violence in coming days.

The death toll from a week of violence in South Sudan has likely surpassed 1,000 people, though there are no firm numbers available, he said. The number of internal refugees has likely surpassed 100,000, said Lanzer, who is seeking urgent financial assistance from the international community.

The violence began late on Dec. 15. South Sudan President Salva Kiir, an ethnic Dinka, said last week that an attempted military coup had triggered the violence, and the blame was placed on former Vice President Riek Machar, an ethnic Nuer. Other officials have since said a fight between Dinka and Nuer members of the presidential guard triggered the fighting, which spiraled across the country.

President Obama over the weekend sent a letter to congressional leaders letting them know he may take further military action in South Sudan to protect U.S. citizens, personnel and property.

Fighting continued over the weekend, as the central government acknowledged it has lost control of Bentiu, the capital Unity, a key oil-producing state. East African leaders are leading diplomatic efforts to avoid a full-blown civil war. South Sudan experienced decades of war with Sudan, which it peacefully broke away from in 2011.

One analyst suggested South Sudan's unrest is partly a problem of the Obama administration's own making.

"[National Security Adviser] Susan Rice has invested an enormous amount of energy in helping South Sudan to separate from northern Sudan after 25 years of civil war and violence, so we helped install the current president, we've given them over 600 million dollars worth of aid and we've been the country to prop them up during this period of transition," said Gen. Bob Scales, a Fox News military analyst.

But Deputy National Security Adviser Ben Rhodes pushed back on the comment.

"We are proud of the instrumental role we played in supporting a peaceful referendum on independence in South Sudan, which implemented the comprehensive agreement that was reached in 2005. Support for self-determination in South Sudan has been broad and bipartisan for many years," he told Fox News.

The White House also issued a strongly worded statement to leaders of the warring factions over the weekend, after the president arrived in Hawaii for his holiday vacation.

"Any effort to seize power through the use of military force will result in the end of longstanding support from the United States and the international community," the statement said.

Fox News' Jennifer Griffin and Doug McKelway and The Associated Press contributed to this report.