Van Gaal is coaching the Netherlands until this weekend when the 2014 World Cup concludes, with his team playing in either the final or the third-place play-off.
United’s other World Cup participants, including Wayne Rooney, Juan Mata, David de Gea and Shinji Kagawa, as well as new signings Luke Shaw and Ander Herrera, will also depart for the United States on 18 July.
But Dutch striker Robin van Persie is not expected to link up with the rest of the squad until August.
United will face Los Angeles Galaxy on 23 July before playing games in the International Champions Cup against Roma, Inter Milan and Real Madrid.
Should they reach the final of that competition - which also features north-west rivals Liverpool and Manchester City - they will play in Miami on 4 August.
A United statement read: "Fresh from his exploits at the 2014 FIFA World Cup, new manager Louis van Gaal will be part of the full tour with his first match in charge of United taking place against LA Galaxy in the Chevrolet Cup at the Rose Bowl on Wednesday, July 23.
"Many of United's World Cup players will also be in attendance for the duration of the tour including Wayne Rooney, David de Gea, Shinji Kagawa and Juan Mata.
"As well as the return of familiar faces, new signings Ander Herrera and Luke Shaw will also be part of the travelling squad to make their Manchester United debuts."