Mauritania, who have never qualified for the Africa Cup of Nations, are among the 15 countries who could secure places at the 2019 tournament this weekend.
The team will be assured of a top-two finish in Group I and qualification if they defeat Botswana in Nouakchott in their penultimate group game.
Cameroon qualify automatically as hosts, and Madagascar have secured their place at a Nations Cup for the first time after qualifying last month along with Egypt, Senegal and Tunisia.
The Mauritanians travelled to Botswana for the first round of qualifying in June last year and won 1-0 through an Abdallahi Soudani goal.
A single goal
While Mauritania have won three of four games in a group completed by Burkina Faso and Angola, Botswana have lost three, drawn one, and not scored a single goal.
Botswana's only previous Nations Cup visit to Nouakchott resulted in a 4-0 defeat 12 years ago.
Elsewhere, South Africa need a win and Nigeria a draw from their Group E clash of former champions in Soweto to be certain of qualification after both missed the 2017 tournament.
Odion Ighalo, the top scorer in 2019 Nations Cup qualifying with six goals, will be missing for Nigeria through injury
Both countries will secure finals places irrespective of the result if Libya lose in the Seychelles.
Egypt against Tunisia in Alexandria is another high-profile fixture, even though both have already booked finals places from Group J.
Some of the stars from the African Champions League winners Esperance of Tunisia and runners-up Al Ahly of Egypt have been selected as the Pharaohs seek revenge for a 1-0 loss in Rades.
Guinea and Uganda will be sure of places among the 24 finalists in Cameroon provided they do not lose at home.
Complete a double
Guinea have a Group H top-of-the-table clash with Cote d'Ivoire, who will be without injured Crystal Palace star Wilfried Zaha as they take on a team who beat them 3-2 in Bouake.
In Group L, Uganda, who share with South Africa the record of not having conceded a goal in 2019 qualifying, will be confident of securing at least a point against Cape Verde in Kampala having beaten them 1-0 away.
If Uganda triumph, Tanzania, whose only previous Cup of Nations appearance was 38 years ago, can accompany them from Group L by collecting maximum points in Lesotho.
Mali will go through from Group C should they complete a double over Gabon after winning 2-1 in Bamako.
For Gabon to qualify, they must triumph in Libreville and hope third-place Burundi lose away to South Sudan in Juba.
Away victories for Algeria and Benin over Togo and the Gambia respectively would secure qualification from Group D while Zimbabwe need a draw in Liberia to advance from Group G.