Van Gaal, who has been the favourite to take charge of the Old Trafford side following David Moyes' sacking, has reportedly held talks with United chief executive Ed Woodward and has agreed provisional terms on a deal worth around 7 million-pound-a-season.
With the growing demand to appoint the job on full-time basis to interim-boss Ryan Giggs and with United bosses also considering a possible move for Bayern Munich boss Pep Guardiola, the Dutchman has issued the one-week ultimatum to the Premier League club, the Daily Star reported.
Despite being the firm favourite to take charge of United, Van Gaal is reportedly in danger of losing patience with the World Cup looming and has told his close friends that he does not want to be kept waiting and wants the club to resolve his immediate future as soon as possible.
A source close to Van Gaal said that the Dutchman knows that he is in a strong position but realises the longer the matter takes to get resolved the more doubts would emerge.
The source said that Van Gaal knows that he is not the only person under consideration for the job as other names have also been mentioned, but the former Barcelona coach cannot wait for too long as it may affect his plans for Brazil.
The source also said that Van Gaal has made it clear to United that the middle of next week needs to be the deadline if the club wants him.
Although Van Gaal has given United a cut-off point in terms of giving him the job, the club has refused to put a time scale on appointing their new manager as they are still smarting from what happened with Moyes and know that they cannot make he same mistake again, the report added.