The Dutchman is the favourite to replace the sacked David Moyes at the end of the season, with prominent newspaper De Telegraaf claiming on Saturday morning that the 62-year-old agreed a deal on Friday.
The report said that Van Gaal met United chief executive Ed Woodward and a member of the Glazer family, the club's owners, at his private villa in the Algarve.
It added that the former Barcelona and Bayern Munich coach, who will lead Holland at this summer's World Cup, would be free to choose his own backroom staff, claiming he would likely take Patrick Kluivert as his number two.
But United, who have put Ryan Giggs in charge until the end of the season, denied the reports, with a spokesman saying: "There is nothing to report. We have not signed a new manager. When we have something to report, we will announce it."
Any move for Van Gaal would now appear to be a contradiction of the wishes of former manager Sir Alex Ferguson.
The Scot, whose retirement teed up the appointment of Moyes - a decision he was a driving force behind - on Friday appeared to put his weight behind Giggs getting the job on a full-time basis.
"I think that he [Giggs] is the one man they should go to really,'' Ferguson said at a charity dinner.
"He's got 20-odd years of experience at Manchester United. I signed him as a kid at 13 years of age.
"He's gone through the gamut of emotions at the club - he's experienced all the highs and lows."
Giggs has immediately tried to evoke memories of former eras at Old Trafford, by installing fellow members of the 'Class of 92' - Nicky Butt, Phil Neville and Paul Scholes - on his staff.
"He knows exactly what's needed to be a Manchester United player and I was so pleased he brought Paul Scholes back in, and Nicky Butt of course - two great professionals," Ferguson added.
"They understand the club, they are hard workers, they are straight as a die. So you have got the right combinations there, there's no doubt about that."