The U.S. Africa Command has asked Washington to send a small group of military advisers to Nigeria to assist its military's fight against the Islamic insurgency Boko Haram, it said in a statement Friday.

At the request of the Nigerian government, the U.S. Africa Command's Brig. Gen. Donald Bolduc sent staff in recent months to conduct a preliminary assessment to determine what is needed and what could be recommended in assisting select Nigerian units, the command said.

"The types of mission sets envisioned under these proposals would likely involve a platoon-sized element operating in a strictly advise-and-assist capacity, much like the previous operations suspended in Nigeria in 2014," said a statement from Africa Command. "U.S. military forces are not currently, and are not planning to operate in an offensive capacity in the Lake Chad Basin region. Our mission is always to enable African partner nations to lead the fight against violent extremist organizations via cooperative, regional approach."

Boko Haram's six-year-old uprising has killed at least 20,000 people and forced more than 2.8 million people from their homes in Nigeria, Cameroon, Niger and Chad, according to Amnesty International and the United Nations. The Nigeria-based extremist group last year pledged allegiance to the Islamic State group.

Attacks by the extremists increased early last year in Nigeria's neighboring countries that are now contributing to a multinational force formed to stamp out Boko Haram.

U.S. Special Operations Forces have been assisting these Lake Chad basin countries with advisers, training and logistical support.

Nigeria curtailed U.S. advisory efforts in 2014 under then President Goodluck Jonathan. When the country's current President Muhammadu Buhari took office in May he pledged to halt the Islamic uprising.

In January, the U.S. donated 24 mine-resistant, ambush-protected vehicles to Nigeria's military, for use in the fight against the insurgents.

The assessment is now being vetted by the U.S. Departments of State and Defense, which will determine the size and scope of the proposed advise-and-assist mission, according to Africa Command. Nigeria is also working on what it requires for the mission, as part of the process, according to Africa Command.

Once decisions are finalized between Nigeria and the U.S., there will still be an extended period of planning, Africa Command said.