Serhou Guirassy was the Guinea match-winner against the Democratic Republic of Congo. AFP
The 28-year-old France-born star scored off a cross to the far post, slamming the ball past goalkeeper Dimitry Bertaud.
Guirassy has scored six times in AFCON qualifiers to lead the Golden Boot race, with four-goal Moroccan Brahim Diaz his closest challenger.
Victory lifted Guinea to nine points, two more than Tanzania, and the west Africans will join already-qualified DR Congo at the finals if they avoid defeat in Dar es Salaam on Tuesday.
Defeat ended a run of eight straight qualifying victories without conceding by the Congolese, who finished fourth at the 2024 AFCON having eliminated Guinea in the quarter-finals.
Earlier, Tanzania defeated bottom team Ethiopia 2-0 in Kinshasa through goals from Simon Msuva and Feisal Salum.
Msuva scored with a near-post header off a corner on 15 minutes and Salum nodded into the net at the second attempt 16 minutes later after his first effort was parried by goalkeeper Seid Habtamu.
Guinea and Tanzania are among 11 countries who will be competing on Monday and Tuesday for the last five places at the 24-nation African football showpiece.
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