The Red Devils have been tracking the experienced Belgian for some time, and have been on the verge of sealing an £11m raid for a while.
But with a hold up in the potential deal, stemming from Arsene Wenger’s desire to get a replacement for his captain in, Barca have emerged as rivals.
The Spaniards are undergoing a major rebuild, with Vermaelen seen as a wise addition after the retirement of club idol and ever-present centre-back Carles Puyol.
But despite the illustrious nature of the Camp Nou outfit, United are sure that they will win the battle.
Vermaelen is said to be desperate to leave Arsenal in the coming weeks after enduring a difficult 18 months at the club in which he has featured infrequently.
Louis van Gaal has earmarked him as the ideal man to become a central figure in his new back three, with Rio Ferdinand and Nemanja Vidic having both left on free transfers.