Zambia were forced to a 1-1 draw by visiting Congo in a Group E game played on Wednesday.
After a goalless first half, Zambia shot into the lead through Winston Klengo in the 60th minute.
But with 15 minutes remaining, Jordan Massengo equalized for Congo to make sure both teams shared the spoils.
With the result, Congo on five points, same as Zambia but ahead on goals difference, still top the group.
Both teams will square off on Sunday in the return leg which comes up in Brazzaville.
In the Group E other game, Guinea-Bissau, playing at home, defeated Kenya 1-0 to go third on four points.
The only goal of the goal was scored by Idrissa Camara in the 15th minute.