The 30-year-old has made just three appearances since injuring his knee after scoring a hat-trick in United's Champions League win over Olympiakos in March, and there had been doubts over his fitness ahead of the tournament in Brazil.
|MAN UNITED LATEST
|11/10||Robin van Persie is 11/10 with Bet365 to be Netherlands' top goalscorer at World Cup 2014|
But the former Arsenal man has admitted that, both physically and mentally, he is raring to go as his country chase their first World Cup title.
"I'm feeling good," he is quoted by the Guardian. "Mentally I'm fresh. If you play a full season you can be a little bit tired at the end of the season. But I'm fresh, the knee is fine as well so I'm looking forward to it."
"I'm 100 percent. It's just that I need a full game now. We have three friendlies to play [and] my last game against Southampton was 67 minutes so hopefully I can play a bit more."
Van Persie has spent plenty of time with national coach Louis van Gaal during his injury lay-off, with the pair spotted together numerous times in recent weeks.
Van Gaal, who is set to become David Moyes' permanent successor at Old Trafford, has hinted at a possible change of formation for the World Cup after talking to his star striker, but Van Persie would not be drawn on any possible tactical surprises.
"It's a difficult question – you will see how we will play.
"I can't comment on that, maybe later – you will see. In the near future you will see."