United have not made any significant signings since David Moyes replaced Sir Alex Ferguson as manager, but it is being reported in Spain that the club have agreed to meet the 36 million euro clause to sign Athletic Bilbao midfielder Ander Herrera.
United are opting not to respond to the speculation, although it is claimed by Deportes Cuatro that part of the deal will involve the Red Devils playing a friendly at Bilbao's new San Mames stadium in 2015.
Baines told Everton officials last week of his desire to join United.
However, Press Association Sport understands Baines reported for international duty with England at their St George's Park headquarters on Monday lunchtime.
While Baines could easily get back to the north-west from Burton, England boss Roy Hodgson expressed the hope last week that his players would have their transfer business done before they linked up ahead of World Cup qualifiers with Moldova and Ukraine.
Herrera played twice against United in 2012 as part of the Bilbao side that was so impressive in dumping them out of the Europa League, scoring at Old Trafford in the process.
Although the 24-year-old's two goals in 63 Primera Division appearances is not that impressive, Moyes feels Herrera can add the drive to his midfield which was notably absent during Sunday's 1-0 defeat at Liverpool.
At present exchange rates, the transfer would cost £30.53 million, just less than the club record £30.75 million United paid for Dimitar Berbatov in 2008.