The Three Lions begin their qualification push against Moldova on Friday, as they aim to reach the 2014 edition of the competition held in Brazil.
But the 29-year-old, who made his England debut eight years ago against Sweden, admits he is unlikely to be around four years down the line.
"Will this World Cup be my last? Probably. Have I been thinking about that? Yes," Defoe told the London Evening Standard.
|OFF TO A FLYER
|10/3||Jermain Defoe is 10/3 to score first against Moldova with Bet365|
“As a youngster when you’re playing on the streets with your friends and watching World Cups, you want to be a part of it. To get a chance to play in another one will be a dream.”
England recently moved up to third in the Fifa rankings despite a disappointing Euro 2012 showing, but the Tottenham striker insisted such accolades are not as important as winning tournaments.
“It’s good to be third and we should be there. People talk about them but they don’t really mean anything because it’s about winning matches," he added.
“It’s important for us to win games and just qualify. That’s what we have to do. We haven’t reached a semi-final for a long time.
“At the Euros we felt so close and were knocked out on penalties [against Italy], but it was another quarter-final. It’s important we bounce back and start the World Cup campaign with a win.”
And the Tottenham man has been spurred on to win the game on Friday as he will hopefully be celebrating his 50th appearance for England.
“It will mean the world. It is something I have been speaking about for a while with my family,” he said. “Not many players can say they have won 50 caps but if we win the game it will be even better.”