In a notification to Congress, President Barack Obama said an advance force of about 90 military personnel began deploying on Monday to Cameroon, with the consent of the Yaounde government.
The troops will "conduct airborne intelligence, surveillance and reconnaissance operations in the region," Obama said. "These forces are equipped with weapons for the purpose of providing their own force protection and security, and they will remain in Cameroon until their support is no longer needed."
U.S. officials, speaking on condition of anonymity, said the troops would provide intelligence to a multi-national task force being set up to fight Boko Haram and composed of troops from Nigeria, Niger, Cameroon, Chad and Benin.
Boko Haram, which wants to carve out an Islamist caliphate and has allied itself to Islamic State, earlier this year stepped up cross-border attacks on Nigeria's neighbors.
On Sunday, two female suicide bombers killed nine people in the town of Mora in Cameroon's Far North region, employing a tactic increasingly favored by Boko Haram.
The American officials said the U.S. soldiers would deploy initially to the city of Garoua in northern Cameroon, not far from the Nigerian border. The force will include Predator drones for surveillance, they said.
The White House said the move was not in response to any changed assessment of threat in the region.
The United States has no combat troops in Africa, but has been increasing support to allies in the region battling Boko Haram.