The Red Devils have been widely criticised for their style of play this season, and the Dutchman says that they will look to strengthen the squad in the "difficult" window.
Louis van Gaal wants to add to his Manchester United squad in the upcoming transfer window but says January is a "more difficult" market than the summer.
United sits third in the Premier League table ahead of Saturday's home game against West Ham but, despite being just one point adrift of league leader Manchester City, Van Gaal has faced criticism for his side's functional and often underwhelming recent performances.