"We aim to reach the final four of the upcoming World Cup, but it will be a very difficult job," said the explosive former Barcelona, Ajax and Bayern Munich coach on Friday.
"My assignment includes rejuvenating this squad, but then there has to be quality and positive results as well."
"It's an honour and challenge that the Dutch federation (KNVB) has asked me for a second term, after all this is the job I have been waiting for."
The charismatic 61-year-old with the distinctive quiff has replaced Bert van Marwijk who stepped down after the disappointing Euro 2012 where the Dutch lost all three group stage matches.
Van Gaal, who signed a two year deal, has added former players Danny Blind and Patrick Kluivert to his technical staff.
He began last week by omitting hard-tackling midfielder Mark van Bommel from his squad for his first match, a friendly against Belgium next Wednesday.
Van Gaal admitted that he had spoken to Ajax Amsterdam and Liverpool before accepting the Dutch job
"I spoke with Liverpool because it is a great club and I never worked before in the Premier League," said Van Gaal who has not coached since he was sacked by Bayern Munich in April 2011.
Van Gaal's previous stint ended disastrously as his side missed out on the 2002 World Cup, the only time the Dutch have failed to qualify for a major tournament in the last 24 years.
He said he had not spoken to his predecessor about the widely-reported internal squabbling which plagued the Dutch squad in Poland and Ukraine.
"I haven't spoken to Bert or members of his technical staff because I want to start without any prejudices," said Van Gaal. "From the outside I also have ideas what happened but I want to know it from my players."
