Vieira, whose career has been plagued by injuries, won the last of his 107 caps for France in a friendly against Nigeria in August but his last appearance in an official match was September 2007 in a Euro qualifier against Scotland.
"I set myself an objective, I want to go to the World Cup," the 33-year-old former France captain and midfielder told television channel Eurosport.
"The important thing for me is to go to Manchester City and to show the coach (Roberto Mancini) I'm the same player than when he was in charge of Inter," he added.
"After a year in Turin and three and a half years in Milan, it's over. To go to the World Cup I need playing time and I can't reach my objective with Inter where I'm not a first choice player."
Vieira, who was a member of France's victorious squads at the 1998 World Cup and the 2000 European championship, won three Premier League titles and three FA cups in nine seasons with Arsenal before moving to Juventus in 2005 then Inter Milan the next year.
"As a man and as a coach, I'm not happy because he is a fantastic man and a great player but I could say I'm happy because he is happy," Mourinho told Eurosport.
