Fans of both teams have descended on Khartoum for the match
Egypt and Algeria are both convinced they will be heading to the 2010 World Cup after Wednesday's winner-takes-all clash in Sudan.
The build-up has been dominated by angry words and violent action, a symptom of the value of the prize and the history between the two countries.
Egypt are on a roll, after grabbing a last-minute goal in Cairo at the weekend to force the play-off.
But Algeria know they will have the backing of most local fans in Sudan.
Algeria's players were rattled by their treatment in Cairo, where their bus was attacked and several players injured.
They are trying to use that as a motivating force for the squad.
In contrast, Egypt coach Hassan Shehata talks of employing more cautious tactics for this one-off game.
Powerful Egyptian defender Wael Gomaa is back for the Pharaohs
The Pharaohs start as slight favourites to secure the last World Cup spot available for an African team.
Defender Wael Gomaa returns to the squad after missing the final group match through injury.
Influential midfielder Hosni Abd Rabou should be back to full fitness too.
Algeria in contrast will be without their suspended goalkeeper Lounes Gaouaoui.
But the defender Majdid Bougherra was full of fighting talk, laughing as he said his team was "ready for the war!"
He might have been joking, but there is considerable concern about this fixture, after a series of violent incidents between Algerian and Egyptian fans in both Cairo and Algiers.
Sudanese football fans are mainly backing Algeria
"To tell you the truth I am worried," the Egyptian board member Hazem el Hawary told BBC Sport.
"There is a lot of heat between the two sets of fans, and there must be a lot of effort made by the Sudanese side to maintain security."
15,000 policemen will be on duty for the match, with 35,000 supporters expected inside the Al Merreikh stadium in Omdurman.
The winner will go to the World Cup, with extra time and then penalties on the cards if the teams cannot be separated after 90 minutes.
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