African leaders agreed on Wednesday to form a $3 trillion continental free-trade zone encompassing 1.2 billion people. However, its two biggest economies, Nigeria and South Africa, did not sign up, Reuters reports. The African Union started talks in 2015 to establish a 55-nation bloc that would be the biggest in the world by member states. The aim is to increase intra-regional trade, which sits at a measly 15 percent of Africa’s total commerce. Rwandan President Paul Kagame, host of an AU summit in Kigali, declared the meeting a success after 44 African nations signed up to establish the free trade bloc within 18 months.