The Red Devils travel to Belgrade eyeing a return to winning ways in Group A after opening with a 2-0 win over Wales in their first qualifier before being held to a 1-1 draw at home to Croatia last time out.
Serbia are seeking to continue the momentum of their 6-1 hammering of Wales and lead the group on four points, ahead of the fancied Belgians on goal difference.
Tomorrow's [Friday] match could be crucial to deciding the outcome of a fiercely competitive section, and Vertonghen believes the visitors have reason to be optimistic.
"The match in Serbia will be one of the hardest, but everyone knows how important this is," the Tottenham defender told reporters.
"We'll go for the three points, but must be sharp in the defence.
"Serbia is starting a new phase where a lot of new players must be integrated.
"It looks like the situation we were in a few years ago and everyone knows how hard that is. We must take advantage of that."
Belgium will be without the in-form Marouane Fellaini.
The Everton midfielder has been pivotal for his side this season but a knee injury sustained against Wigan last week will keep him out of both tomorrow's match and Tuesday's clash with Scotland in Brussels.
Serbia, meanwhile, will be without goalkeeper Vladimir Stojkovic after he broke his collarbone in a league match for Partizan Belgrade on Sunday.
Udinese's Zeljko Brkic is expected to deputise between the sticks.
Group A also witnesses a mouth-watering 'Battle of Britain' contest tomorrow [Friday] as Wales and Scotland look to get their stuttering campaigns up and running in Cardiff.
Both sides have endured disappointing starts to their campaign with the Scots drawing against Macedonia and Serbia and the Welsh occupying bottom spot after defeat to Belgium was followed by their horror show against Serbia.
Wales have been given a boost on the eve of the contest after Gareth Bale was passed fit to play after suffering a heel problem, and manager Chris Coleman will be wanting a big performance from the Spurs winger as he bids to avoid a fifth straight defeat at the start of his tenure.
Wales coach John Hartson admits Wales' return of one goal from their opening two matches is a concern, but has backed his players to come good.
He said: "If we weren't really creating chances I'd be more worried.
"Hopefully we can create plenty of chances, get the crowd behind us and we can score some goals."
Celtic midfielder Kris Commons, meanwhile, has stressed the importance of Scotland taking maximum points if they are to have any chance of qualifying for the 2014 finals.
"We need to win against Wales first and then we can see about Belgium after that," the Scotland forward said.
"After two draws it is important to get a win and the way the group is set up, that could put us right into contention.
"The next two games are really important but it was always going to be a group where countries take points off each other."
Croatia travel to Macedonia in tomorrow's [Friday] remaining Group A clash.
The Croatians defeated Macedonia in their opening game before drawing in Belgium, while Macedonia have just a point to show from their first two games.