The Belgian defender has been on the verge of completing a move to Old Trafford from Arsenal for some time, with the deal seemingly being held up by the Londoners’ desire to get in a replacement for him.
This has left the door ajar for Barca, who are now tracking the 28-year-old.
The Spaniards are desperate to bolster their backline before the new season starts after a few seasons of possessing a lack of options in the area.
Frenchman Jeremy Mathieu has already been signed, but Vermaelen is now seen as another option with Carles Puyol having retired.
It is understood that United is a more appealing option for the 28-year-old due to a greater chance of first-team football, but Barca may well be able to convince him to become a part of their new project.
Vermaelen is still Arsenal’s captain, but he’s been an infrequent starter for the last 18 months.