He, however, observed that the demand was heavy especially as he is reluctant to interfere with the functions of other arms of government.
Kanu, who is currently standing trial for treason, is in custody of the Department of State Services (DSS).
The President made the promise on Friday, November 19, while receiving a group under the aegis of Highly Respected Igbo Greats, led by First Republic parliamentarian and Minister of Aviation, Chief Mbazulike Amaechi, at State House, Abuja.
He said the unconditional release of Kanu runs contrary to the doctrine of separation of powers between the Executive and Judiciary.
According to a statement by presidential spokesperson, Femi Adesina, Buhari told the 93-year-old statesman that, “You’ve made an extremely difficult demand on me as leader of this country. The implication of your request is very serious. In the last six years, since I became President, nobody would say I have confronted or interfered in the work of the Judiciary.
God has spared you, and given you a clear head at this age, with very sharp memory. A lot of people half your age are confused already. But the demand you made is heavy. I will consider it.”