Capello warned James earlier in the week, that he will only brin fully-fit players to South Africa.
James has been struggling with a knee injury in recent weeks.
“I’m not concerned about my knee and it will not be a reason why I won’t be fit for the World Cup,” James told the Daily Mail.
“If the injury was a serious one I’d be looking to rest for a number of weeks and miss a load of games for Portsmouth.
“But I don’t need to and that should tell you everything. By managing the situation, I am able to play every week.
“But I missed England squads earlier in the season because I couldn’t train the way the manager (Fabio Capello) wanted me to.
“He has a very strict policy. If you can’t do their training before a game he won’t pick you and that’s fair enough.
“And I missed the last squad for Brazil because it was considered more sensible to give me a two-week break.
“The same went for a number of the lads. For me, it has proved a good decision because the knee is getting better all the time.”