Brown had been a regular member of Fabio Capello's squads, but injuries have cost him his place on the plane for South Africa.
The 30-year-old missed the last two months of the season with a broken foot and Capello has decided not to pick Brown in his provisional 30-man squad.
"I was disappointed to be omitted from the squad," Brown told the Sunday Mirror.
"The World Cup is the pinnacle of any footballer's career and as a kid you always dream about pulling the England shirt on in the World Cup final.
"But I have not played any football for the past few months. I'll definitely be watching and keeping my fingers crossed for the team.
"I think the squad is really strong and we have a really good chance of having a successful tournament."
Meanwhile, Brown believes United team-mate Wayne Rooney is the best player on the planet and that he will thrive on the World Cup stage this summer.
"I wouldn't swap Wayne Rooney for anyone," added Brown.
"He was a great player when he first came to United, but he has got better every year and I think this season he has put himself right up there with the best players in the world.
"At the moment he isn't one of the best - he's the best.
"I know I am biased but there isn't a weakness to his game and he has been scoring goals for fun.
"Ronaldo is fantastic, but maybe leaving United has given Wayne the chance to play in his favourite position as a striker and he has been unbelievable.
"The World Cup is his kind of stage. He will love the challenge of trying to beat the best defenders."