Manchester United have been given the green light to move for Thomas Vermaelen after Arsène Wenger admitted the Arsenal captain could leave the club before the close of the transfer window. However, United face competition from Barcelona for the Belgian defender’s signature with Arsenal preferring to sell abroad and not to a direct rival.

Although the 28-year-old has a minor hamstring injury he suffered with Belgium during the World Cup it is understood this is not an issue in any potential deal.

Vermaelen, who would cost around £12m, would be the first signing identified by Louis van Gaal since he became manager, as Luke Shaw and Ander Herrera were selected by the previous manager, David Moyes. Their respective transfers were signed off by Van Gaal.

The Dutchman wants to sign two central defenders following the departures of Nemanja Vidic and Rio Ferdinand and is an admirer of Vermaelen, who would play as the left-sided centre-back in a 3-5-2 formation.

Arsenal would prefer to sell abroad though, with Barcelona firmly interested in making a move.“At the moment, Thomas Vermaelen is here,” Wenger said. “He is injured at the moment for a short-term injury. It [a transfer] could happen, yes. It’s a possibility that he goes. If he goes, we have to replace him because he’s an important player in our squad.”

Asked if he expected Vermaelen to depart, Wenger said: “No, I expect him to stay but he, of course, did not play enough games last year. For me he’s a very important player but I couldn’t guarantee him the games he wanted last year.”

The Frenchman would not be drawn on who may replace Vermaelen as captain. “I haven’t solved that problem yet because I am not sure that he will stay. We’ll see,” said Wenger who did not want to state if the defender would remain the club leader if he were not sold. “I don’t have to make it [the decision] today.”

With Wenger needing to replace Vermaelen if he does depart, the manager could ask for Chris Smalling in part-exchange, though Van Gaal may not accept this as the 24-year-old is one of only three senior centre-backs at United.

Wenger did admit he wants to strengthen further in the window. “I am very happy because I did what I wanted and I am still hoping to do more,” he said. “It is 1 August and the transfer window closes on the 31st. It is a long time. We are a bit ahead of what we usually do because the availability on the market was bigger than before.”