The £75 million striker nursed a slight ankle complaint during the international break, with the injury enough to keep him out of a 2018 World Cup qualifier with Bosnia-Herzegovina.
Fellow countryman Vertonghen is convinced that the 24-year-old has shaken off any fitness issues and is raring to go ahead of the resumption of Premier League action this weekend.
The Tottenham defender told reporters on Lukaku: “The goal he got against Cyprus was so typical, a ball in behind and he brushed defenders off and smashed the ball into the net. I am sure he will be fine for Manchester United at the weekend.
“He used the first week with us to get fit. He was injured, I spoke to him and his ankle wasn’t in good shape but he has used the time well to recover and he is back and fit again.”
Lukaku’s effort against Cyprus was his 16th of the season for club and country.
An immediate return has been offered to United on their sizeable show of faith, with the target found 11 times in 10 outings.
He currently leads the race for the Premier League Golden Boot, with his seven-goal haul placing him one clear of Manchester City’s Sergio Aguero, Chelsea’s Alvaro Morata and Tottenham’s current holder of that prize, Harry Kane.
Vertonghen expects the battle of the proven marksmen to go down to the wire, with there little to choose between some of the finest finishers in the business.
He added: “In my eyes it is difficult to split them.
“I think they will keep playing for the Golden Boot until the last game of the season like they did last year.
“Obviously Romelu is in great form. Harry is special as well. I can’t find the words to describe them enough.”
Lukaku and United will get a chance to lay down a marker to their Premier League rivals on Saturday as their trip to Anfield is the lunchtime kick-off, meaning that they can take to the top of the table before the likes of City, Spurs and Chelsea return to domestic competition.