Manchester United striker Van Persie is hoping to get back to his best in Brazil after a frustrating and injury-hit season at Old Trafford.
The 30-year-old has scored in friendlies against Ecuador and Ghana in recent weeks as he steps up his recovery from a knee problem.
Van Persie missed six weeks of action towards the end of United's campaign, returning only for their last three Premier League games. He had been troubled by thigh problems earlier in the season.
Van Gaal kept a close eye on Van Persie's most recent rehabilitation having been given permission by United -- the club that would later appoint him as manager -- to bring him to a training base in the Netherlands.
The 62-year-old, who will link up with Van Persie full time at United next season, said: "He is not 100 percent, but we have two weeks to go. I think he will be 100 percent.
"He is coming out of injury but we built him already up in our federation, our medical department.
"It was under the permission of David Moyes, so we could control him, he has worked very hard.
"Then he played two matches of 20 or 30 minutes and the last match 70 minutes. We did not expect that as the injury was bad.''
Van Persie is likely to be given another run-out as the Netherlands take on Wales in Amsterdam on Wednesday in their final friendly before flying to Brazil.
The Dutch then begin their World Cup campaign against holders Spain in a repeat of the 2010 final in Salvador on June 13. They face Australia and Chile in their other Group B games.
The Netherlands have finished runners-up three times at the World Cup, and Van Gaal feels that past record perhaps places unrealistic expectations on his current squad.
"The purpose is to win the World Cup and the purpose of the board is the semifinals," he said. "I think it's a big purpose -- the purpose is maybe too big an expectation.
"I think this team can beat all, but we can also lose. That's sport and we accept that but it's difficult for the Dutch people to accept."
The pressure, however, is not something that bothers veteran Van Gaal, who has a proven track record of success from his club career with Ajax, Barcelona, AZ Alkmaar and Bayern Munich.
He said: "You do not know Louis Van Gaal! I give myself more pressure than anyone else. I will always win.''