The Nigerian government has appealed against a London court ruling which required it to pay $200m (£155m) to prevent a firm from beginning to seize the country's assets worth $9.6bn.
In August, a British court ruled in favour of the company, Process and Industrial Developments (P&ID).
It had fought a long-running legal battle with the Nigerian authorities over a failed project to build a gas processing plant.
P&ID claims successive Nigerian administrations failed to fulfil their end of the deal, causing it to lose on its investment.
The Nigerian government says the deal was fraudulent and amounted to economic sabotage.