Pentagon spokesman Col. Steven Warren said a "platoon-sized" team of Marines and a C-130 aircraft would be detached from a deployment in Djibouti to travel to Entebbe, Uganda, AFP reported.
"This forward posturing provides the Combatant Commander additional options and the ability to more quickly respond, if required to help protect US personnel and facilities," Warren said, confirming earlier reports.
Warren added that the deployment was made with the awareness of Ugandan authorities.
A 150-member special Marine Corps unit left Monday for a US base in Djibouti, along with cargo planes and helicopters. The total task force focused on evacuating Americans in the violence-ravaged nation of South Sudan consists of 500 troops who are currently stationed at Morón air base in Spain.
The Pentagon has already sent a 47-member task force to Juba to reinforce the US embassy amid fierce interethnic fighting spurred on by a power struggle between South Sudan President Salva Kiir and his former vice president, Riek Machar, that began in mid-December.
US President Barack Obama warned members of Congress on Sunday that American efforts in South Sudan could be ramped up in the coming days as the security of US citizens and others in the East African nation are increasingly put at risk.
People gather at a makeshift IDP camp at the United Nations Mission in South Sudan (UNMISS) compound in Juba on December 22, 2013 where South Sudanese continue to flock as fears of a resumption of fighting in the capital fester. (AFP Photo / Tony Karumba)
An attempted rescue mission waged by the US on Saturday to try and remove Americans currently residing in the embattled nation was aborted after rebel fighters reportedly aligned with Machar opened fire on US planes, injuring four.
Three of those injured are in stable condition at the US military hospital in Germany, while the fourth continues to undergo treatment in Nairobi, Kenya.
As of Monday, around 380 American citizens and 300 others had been evacuated by the US from the city of Juba. Obama sent a letter to select congressional leaders on Sunday, informing them that he may advise the military to increase its efforts.
"As I monitor the situation in South Sudan, I may take further action to support the security of US citizens, personnel, and property, including our embassy, in South Sudan," Obama wrote on Sunday.
Meanwhile, a mass grave containing 75 bodies was found in an area controlled by rebelling troops who support Machar, UN High Commissioner for Human Rights Navi Pillay said on Tuesday.
"We have discovered a mass grave in Bentiu, in Unity State, and there are reportedly at least two other mass graves in Juba," Pillay said in a statement in Geneva.
Preliminary conclusions indicate that all the victims were Dinka soldiers, an ethnic group to which President Kiir belongs. Machar and many of his supporters belong to the country's Nuer tribe.
The suspected ethnic killing comes amid the escalated battle between troops supporting the two rival factions. President Kiir has blamed Machar for attempting a military coup, while Machar has accused Kiir of being "dictatorial" and attempting to carry out purges.
The rivalry is threatening to tip the young country into a full civil war, as reports relay that thousands have died from the recent outbreak of violence.
The United States has much invested politically in South Sudan, as it was the US that played a major role in encouraging the Sudan People's Liberation Movement to break away from the Republic of Sudan in the north of the country, Abayomi Azikiwe, editor of Pan-African News Wire, told RT in an interview.
"In [South Sudan], the US is trying to develop mechanisms for exploiting the oil. The problem is, the United States does not have a lot of resources to invest in the oil industry inside the country."
Azikiwe said that Washington's encouragement of the national split in 2011 was to weaken a Republic of Sudan whose oil resources were largely controlled by China's interests. Yet despite the split of Sudan, the US still cannot dictate its own terms in South Sudan.
The problem for countries seeking to exploit Sudanese oil, Azikiwe told RT, is that any extraction must be a collaboration between Sudan and South Sudan - two nations whose people have not benefitted from the split.
"Both nations have suffered tremendously as a result of the partition and the ongoing instability. Oil production, even in the north, is down to less than 2,000 barrels a day. So the partition has crippled the economies of both the north as well as South Sudan."
