Blatter said the appeal was lodged following the Republic of Ireland's controversial play-off defeat to France, which saw a clear handball from Thierry Henry lead to a late tie winner for the French.
"Naturally [Ireland] were unhappy with what happened and asked very humbly whether they could be team number 33," Blatter said.
"I will bring it to the attention of the executive committee but if we do that, we will also have to bring in Costa Rica."
Blatter also talked about the potential of adding extra officials during the World Cup in South Africa.
"It's possible we will make additional officials for the World Cup but we have to see if it is feasible or realistic. Something has to be done in terms of match control.
"How can it happen that all over the world, through tv cameras, we have seen through a cheating handball that a pass was given for a goal?
"Everyone is asking what is and what isn't fair play. The highest crime in football is touching the ball with the hands."
- Football.co.uk staff