The North African countries are members of the Common Market for Eastern and Southern African (Comesa), one of three groups which are joining forces to set up the free trade zone.
The other groups are the East African Community (EAC) and the South African Development Community (SADC).
The decision was reached at a meeting of African heads of state in the Ugandan capital Kampala on 22 October. The leaders also agreed to co-operate on energy and infrastructure projects.
The EAC already has a customs union while Comesa plans to launch one by December.
Twelve of the SADC’s 15 members launched a free trade zone in August and the community is planning to create a customs union in 2010.
The other countries which are part of the new pan-African trade zone include Angola, Botswana, Burundi, the Comoros, Djibouti, the Democratic Republic of Congo, Eritrea, Ethiopia, Kenya, Lesotho, Madagascar, Malawi, Mauritius, Mozambique, Namibia, Rwanda, the Seychelles, Swaziland, South Africa, Tanzania, Uganda, Zambia and Zimbabwe.