Buhari was also said to have ordered the National Security Adviser and the Nigerian Intelligence Agency to investigate the contractor.
According to Premium Times, Buhari's Chief of Staff, Abba Kyari, earlier this week dispatched a memo directing the Attorney General of the Federation, Abubakar Malami, to terminate the contract.
The President was also said to have ordered the National Security Adviser and the Nigerian Intelligence Agency to investigate how the contractor obtained security clearance for the job without an end-user certificate.
Buhari also reportedly ordered that the contractor should be made to supply items equivalent to the $50 million upfront payment which they received recently.
If the contract had pulled through, the contractor, HSLi, would have received $195 million in payment for the sale of an undisclosed number of special mission aircraft, special mission helicopters and 12 fast intervention vessels for the Nigerian Navy.
The contract was signed off by the Federal Executive Council in December 2017.
A report by Guardian said Nigeria was meant to acquire three helicopters, three aircraft, three big battle-ready ships, 12 vessels and 20 amphibious cars to secure Nigerian waters from the 'Israeli company'.
The deal had been criticised and described as a contract designed to steal, with Amaechi fronting for the government.
Investigations by Premium Times revealed that the contractor, which according to Amaechi is an Isreali company, is not registered as a business entity in Israel. But the company is said to hold close ties with Mitrelli, another Israeli Company which also holds close ties with the minister.
When Amaechi served as the governor of oil-rich Rivers state, he had awarded a $140 million contract to Mitrelli (aka LR Group) to develop a farm in Etche, a suburb of Port Harcourt, the state capital.
LR Group was said to have recently rebranded as Mitrelli as it transitioned into an arms business.
The President's spokesmen Femi Adesina and Garba Shehu did not respond to enquiries about whether Buhari let Amaechi in on the termination.
Also, a spokesperson for the Ministry of Transport, Yewande Shonaike, did not respond to requests for comments about the development.