Beckham said: "The standard in the USA is higher than anyone thinks and expects. America is a great place to play and the standard is improving all the time. People say 'can you play at this level or that level' but it doesn't change me as a player.
"I'm always going to be the same player - whether I'm playing in Spain, England or the USA. That won't affect my game.
"I can switch from playing in the USA at the weekend to then playing on a Wednesday against one of the best teams in the world and the best players in the world.
"I'll always be the same player that, if given two or three yards, I can cross a ball into the danger area. People have said I've lost my pace but I've never had a major amount of pace anyway. I have never really been someone who has gone past players.
"Fitness-wise, I feel I can carry on for a few years. If I felt I couldn't carry on, maybe I'd turn around and retire from international football but that is not the case. Of course, things can change. At the moment I am taking each game as it comes. Who knows what is around the corner? You can have extreme highs and lows.
"I've had those in the last couple of years but I wouldn't be putting myself forward if I couldn't physically do it still. I still feel I can perform at the highest level and it is exciting to play again under Fabio Capello who is a great manager.
"I want to be part of the squad for the 2010 World Cup if at all possible. The manager has already said if I stay fit and I am performing, then I've got a chance to be in the squad."