The Everton midfielder was due to join up with his team-mates in Neerpede on Monday ahead of their clash with Scotland on Friday but has been granted dispensation to stay in England.
As revealed by Goal, the Toffees have verbally agreed a £24 million (€28.3m) deal with United for the Belgian midfielder, who is expected to complete his move to Old Trafford before the midnight CET transfer deadline.
United are also hoping to secure a deal for Everton left-back Leighton Baines, however, the club have valued the 28-year-old at £20m (€23.6m) and are continuing to reject advances from the Premier League champions.
David Moyes is keen to add to his midfield options before the close of the transfer window and reports in Spain claim that United are willing to meet Ander Herrera's €36m (£30.5m) buyout clause, with the 24-year-old now set to undergo a medical ahead of a move from Athletic Bilbao.
Everton, meanwhile, have submitted an offer for Cagliari defender Davide Astori, while Roberto Martinez is also targeting moves for Manchester City duo Joleon Lescott and Gareth Barry, and Wigan Athletic's James McCarthy.