Diogo Dalot scored a pair of goals as Portugal defeated the Czech Republic.
The winners took full advantage of Spain's loss to Switzerland to move to the top of the group.
Portugal will have to beat Spain on Tuesday in order to make the finals.
The second and fourth goals were scored by Dalot's Manchester United teammates.
Having lost their previous Nations League match against Switzerland, Fernando Santos' side responded by winning their next match to keep their qualification hopes alive.
Portugal was in control thanks to Dalot's first-time strike from the cut-back and the finish from Mario Rui.
After being awarded a penalty by the referee, the Czech forward was unable to get a goal before the break.
Right-back Dalot put the game out of reach seven minutes after the restart with a superb left-footed finish from outside the box, before Jota headed in with eight minutes remaining.
In the first half, he had to be treated for a blow to the face he sustained in a collision with the Czech goalie.
The Czech Republic needs to beat Switzerland in their final match to stay in the league.
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