Street vendors sell shoes at the Al-Attaba market in the centre of Cairo, Egypt, on February 21, 2018.

African heads of state have gathered in Kigali, Rwanda, to sign a free trade agreement that would result in the largest free trade area in terms of participating countries since the formation of the World Trade Organization.

Leaders are poised to approve the African Continental Free Trade Area, a deal that will unite the 55 member countries of the African Union in tariff-free trade.

The agreement is touted by the African Union as encompassing a market of 1.2 billion people, and a gross domestic product of $2.5 trillion. It is hoped that it will encourage Africa's trade to diversify away from its traditional commodity exports outside of the continent, the volatile prices of which have hurt the economies of many countries.

"Less than 20 percent of Africa's trade is internal," Rwandan President Paul Kagame, also currently chairperson of the African Union, said in a speech Tuesday. "Increasing intra-African trade, however, does not mean doing less business with the rest of the world."

But, the deal has its critics. It was announced over the weekend that Nigerian President Muhammadu Buhari would not be attending the summit, despite his federal cabinet last week approving the deal. "This is to allow more time for input from Nigerian stakeholders," said an official statement from the foreign ministry.