Buhari made the disclosure during the All Progressives Congress (APC) presidential campaign in Enugu, on Thursday.
He lamented that fulfilling the promise Amaechi made would be difficult.
Buhari, however, said he would try his best to convince the Federal Executive Council members to approve the project.
He said: “Amaechi has made you people a promise and I don’t know how to fulfil it. But I can see how I will fulfil it by getting the Federal Executive Council members to approve it.”
The president said the promise Amaechi made was not presented to the FEC, adding that it would have been proper to get approval from FEC before making it open.
Buhari also thanked the people of the zone for trooping out for his campaign, adding that they should always have faith in Nigeria as they did not have any other country.
He said: “We all must join hands to build a stronger country as we do not have any other country.”
The president reminded the people that his government was determined to fix infrastructure in the country, adding that “if we get the roads done, get the rail lines done, and get other infrastructure done, we will be making progress.”