The 25-year-old was one of six goalkeepers named in Louis van Gaal's original squad for a friendly with France on Wednesday before being cut from the party in favour of Jasper Cillessen and Jeroen Zoet.
Despite the setback, Krul claims a spot in Brazil is not out of the question - provided he can put in some impressive showings for Newcastle between now and the end of the season.
"I'll keep fighting to the end. I've got 10 games left to show them that I'm ready and I think the manager knows what he gets from me," Krul told The Northern Echo.
"I'm going to do my best to show him that I should be on that plane to Brazil."
"He hasn't phoned to explain his decision, but I don't think the manager has to do that."
After going four games without a win, Newcastle have picked up maximum points from their last two games courtesy of victories over Aston Villa and Hull City.
"We've had a bad month and I think we have to be honest about that," Krul continued.
"We have turned it around with two great wins and the only thing I can do now is impress in the next 10 games."
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