United have tabled an opening offer of £26m for the midfielder, who joined the Nou Camp giants two years ago.
Arsenal insisted on having a £25m buyback clause, with a 50 per cent sell-on inserted, after selling Fabregas to the Catalans for £30m.
But Wenger has made no move to re-sign Fabregas, leaving United in pole position to get him.
Barcelona are unlikely to accept the first offer from Old Trafford, which came after Moyes was snubbed by his No.1 target, Thiago Alcantara.“Arsenal insisted on having a £25m buyback clause”
It remains to be seen whether Fabregas, 26, would be prepared to join United having been at the centre of some stormy encounters with the Red Devils while at Arsenal.
Fabregas had been widely rumoured to be the player who threw a slice of pizza at Sir Alex Ferguson after a hot-headed clash at Old Trafford in October 2004.
But Fabregas is said to be one of several stars at Barcelona who have been less than impressed at the huge wages dished out to new Brazilian superstar Neymar which top that of even Lionel Messi.
Meanwhile, Arsenal target Gonzalo Higuain has returned to training with Real Madrid and asked for time to consider his future.
Madrid were willing to sell Argentine striker Higuain for £26m but Arsenal's bid was £3m below that