Reports circulated on Tuesday that the former Barcelona and Bayern Munich manager could be rubber-stamped as David Moyes' successor as early as Wednesday.
But Sky Sports News reporter James Cooper believes United fans will have to wait for a formal announcement confirming the 62-year-old's appointment.
"I think it's a case of when not if, but that 'when' may be a little longer in the future than perhaps we imagined on Tuesday," he said.
"Certainly the information throughout the day was that there might be an appointment today (Wednesday), which coincides with Louis van Gaal taking charge of the Netherlands squad at a training camp this afternoon.
"The received information now is that Manchester United are very relaxed about the situation but we might not get an announcement rubber-stamping Louis van Gaal's appointment as Manchester United manager until perhaps as late as next week.
"He's the man Manchester United want. They have sounded out other candidates but Louis van Gaal is going to be Manchester United's next manager.
"I think Manchester United, quite understandably, want to get this season out of the way. It's been a disappointing season and next week they will unveil Louis van Gaal as their new manager."
Sky Sports' Gary Cotterill, reporting from the Dutch training camp believes it could be the middle of next week until Van Gaal's future becomes clearer - and understands United are not his only suitors.
"My sources from here in the Netherlands say it's quite correct that there will be no announcement this side of the weekend regarding Louis van Gaal going to Manchester United," Cotterill said.
"There won't be any announcement on Monday, nor - by my understanding - on Tuesday. The earliest any announcement will come is Wednesday.
"I also understand that no deal has been done, despite reports. Other clubs do remain in the running to sign him up after he finishes on Netherlands duty after the World Cup - both in the Premier League and inernationally."