The winners of the African play-offs final advance to a six-nation intercontinental tournament in Mexico during March that involves each football region except Europe.
But the losers will bow out of the contest to be among the record 48 nations that take part in the global showpiece hosted by the United States, Canada and Mexico.
Nigeria and DR Congo were among four countries given a second chance to qualify after being the best runners-up from nine African groups.
In the semi-finals on Thursday, Galatasaray striker Osimhen scored twice in extra time as Nigeria beat Gabon 4-1, while Chancel Mbemba snatched a late 1-0 win for DR Congo over Cameroon.
Osimhen, the 2023 African Player of the Year, scored a hat-trick last month in a 4-0 triumph over Benin that enabled Nigeria to squeeze into the play-offs.
The 26-year-old, who continues to wear a protective mask after suffering serious facial injuries four years ago, posed a constant threat against Gabon and could have notched six goals.
On several occasions, he came agonisingly close to scoring before, in the last of 12 minutes added time, he fired wide with only goalkeeper Loyce Mbaba to beat.
"I was gutted after failing to score from that opportunity. It was a bad miss," Osimhen admitted to reporters.
"Sometimes I score amazing goals no one expects and, on other occasions, I miss when people expect me to score.
"I apologised to my teammates after that miss and promised to find the net in extra time, which I did twice."
Nigeria have qualified for the World Cup six times in eight attempts since first achieving the feat in 1994.
'Passion'
The Super Eagles have never missed back-to-back World Cups since their debut and are desperate to atone for a play-off loss to Ghana that deprived them of qualification for Qatar three years ago.
Nigeria are 19 places above DR Congo in the world rankings and favourites to win the clash of the Super Eagles and the Leopards, but Ivory Coast-born coach Eric Chelle is cautious.
"The victory over Gabon means nothing. We now face formidable opponents in DR Congo and, assuming we win, there will be time to celebrate.
"We are trying to create an identity. My players understand what I want and are improving mentally and technically with each international window.
"The key to success over Gabon was passion. It was about working together. We have to rediscover that passion against the Congolese," added the 48-year-old former Mali coach.
While Nigeria have been regular participants at the four-yearly World Cup, the sole appearance by the Congolese came in 1974 when the mineral-rich central African country was called Zaire.
French coach Sebastien Desabre has transformed the always talented but often erratic Congolese into a combative outfit captained by outstanding centre-back Mbemba from Ligue 1 club Lille.
"We have experienced players. What we are putting in place has not happened overnight. We are going to give our all against Nigeria," promised Desabre.
Nigeria have been involved in 16 World Cup qualifying campaigns and DR Congo 12, but the showdown at the 22,000-seat Prince Heritier Moulay El Hassan Stadium will be the first meeting between them.
Bolivia and New Caledonia have secured intercontinental tournament places, Iraq or UAE will represent Asia and Jamaica and Panama are the frontrunners to be the two Central American/Caribbean qualifiers.