In a letter to Congress, Obama said the troops will act as advisers in efforts to hunt down rebel leader Joseph Kony but will not engage in combat except in self-defence.
Pentagon officials said the bulk of the U.S. contingent will be special operations troops, who will provide security and combat training to African units.
The White House said the first troops arrived in Uganda on Wednesday.
Ultimately, they'll also deploy in South Sudan, the Central African Republic and the Democratic Republic of the Congo.
The deployment to central Africa is but the latest sign of an increasing administration focus on the continent, amid increasing concern about shaky governments, civil strife and sprawling regions that have become both havens for terrorists and spawning grounds for piracy.
Long considered one of Africa's most brutal rebel groups, the Lord's Resistance Army began its attacks in Uganda more than 20 years ago but has been pushing westward since. Read More