US President Barack Obama has announced he is deploying 100 "combat-equipped" troops to Uganda to help efforts against rebels of the Lord's Resistance Army (LRA), who Washington accuse of grievous human rights abuses.
The US troops, subject to the approval of national authorities, could also deploy from Uganda into South Sudan, the Central African Republic and Democratic Republic of the Congo, Obama said in a message to Congress.
LRA rebels are accused of murdering, raping and kidnapping thousands of people in the four nations.
Tens of thousands of people have died in their 20-year war with security forces in northern Uganda.
"These forces will act as advisors to partner forces that have the goal of removing from the battlefield Joseph Kony and other senior leadership of the LRA," Obama said, but warned they would not lead the fighting themselves.
"Although the US forces are combat-equipped, they will only be providing information, advice, and assistance to partner nation forces.
"They will not themselves engage LRA forces unless necessary for self-defence. All appropriate precautions have been taken to ensure the safety of US military personnel during their deployment."
The president said a small group of troops deployed on Wednesday and that additional forces will deploy over the next month.
Kony is accused of war crimes and wanted by the International Criminal Court.
The civil war effectively ended in 2006 when a peace process was launched, but Kony and his top commanders continue to commit atrocities in remote areas of neighbouring countries.
General Carter Ham, the head of US Africa Command, said last week that his best estimate was that Kony was probably in the Central African Republic.