The Dutch boss is expected to take over at Old Trafford when his responsibilities with the Holland national team come to a close after the World Cup, with some speculation suggesting a deal between all parties involved has been agreed.
Former manager David Moyes was expected to have in excess of £100m to spend in the transfer market, and it appears likely that van Gaal will be given the same luxury.
Although a creative midfielder has long been thought of as the major priority, the experienced coach really wants a rugged defender to replace Nemanja Vidic.
Hummels is believed to be the name at the top of a list submitted to United by van Gaal, and the club are believed to be ready to attempt a £30m move for the German star.
Other players he also wants include Toni Kroos of Bayern Munich and compatriot Kevin Strootman, who plays for Roma.
Marco Reus is thought to be another target.