Having joined Bournemouth from Sunderland on a free transfer following the Black Cats' relegation from the Premier League, Defoe is focusing on a place in Gareth Southgate's squad for Russia.
Defoe, who netted 15 times in the league last season, will be 35 by the time the tournament comes around and is relishing the opportunity for a second finals appearance, having featured in South Africa seven years ago.
"It's only normal to have one eye on the World Cup," Defoe said.
"Every English player will want to get in to that squad but it's based on merit, so you'll have to play well for your club.
"I'll focus on doing that and then if I get the opportunity to play in the World Cup again, it would be a dream."
In 2010, he scored the lone goal against Slovenia to secure England's passage to the knockout stage, before falling out of favour in Roy Hodgson's squad regeneration.
He earned a recall from Southgate in March and scored upon his return, a 2-0 qualifying win over Lithuania.
Defoe knows, however, he will have to fight for his spot under Cherries boss Eddie Howe.
"It's good competition here and that’s what you want as a player," Defoe said.
"It's no different to Tottenham because there were always four top forwards who would go away with their national team and England.
"It keeps you on your toes and you know that you have to work hard to get that opportunity and when you get it, you have to take it. It's as simple as that."