Van Gaal remains the bookmakers' favourite to replace David Moyes, who was sacked last week.
Ryan Giggs has been put in charge until the end of the season, and United beat Norwich 4-0 in his first match last Saturday.
Van Gaal will be Netherlands boss at this summer's World Cup, but will then step down. He had been linked with Tottenham but it is understood he has held productive talks with United.
United though are keeping their options open with other candidates still in the frame.
It has not been confirmed who they are, but the likes of Atletico Madrid coach Diego Simeone, who has guided his team to the brink of La Liga title and the semi-finals of the Champions League, Borussia Dortmund coach Jurgen Klopp and even Giggs himself could be in the frame.
Carlo Ancelotti, the Real Madrid boss, is another linked with a move to Old Trafford, although he says he is staying in Spain.
"I haven't spoken with anyone and I don't need to speak to anyone. I'm very happy here," he said ahead of Real's Champions League semi-final with Bayern Munich.
Moyes was sacked after a disappointing season in which United lost 11 matches and failed to qualify for next season's Champions League.
They did reach the quarter-finals of the Champions League where they were knocked out by Bayern Munich, and there was no joy in the domestic cups either.
Moyes, recruited from Everton last summer, paid the price, with the owners losing patience with the perceived lack of progress.
The new manager is likely to have a transfer fund of over £100m to spend to strengthen the squad in the summer.
And Giggs is confident that United will be challenging for the Premier League title again next season.
He said: "We've got everything in place to have a successful season next year. We've certainly got the players.
"It's going to be hard, obviously, because we've had a tough season and obviously the lads at Liverpool have improved and other teams around us have improved.
"It won't be easy, but I'm confident."
He added on claims that United are now a side in decline: "We won the league last year. The year before we lost it on goal difference, the year before that we won it.
"Where did Liverpool come last year, seventh? Who would have said they would be where they are this year, so a lot can change."