Yeah but when he was fighting sasuke and Oro came up, he revealed that he had been looking for the sword and he made it seem like he had wanted to use it undo the seal that sarutobi had placed upon his arms.
Thats why i think it could undo seals. Whether itachi could undo the seals, am not sure but why have a sword and learn how to seal yet not care to learn how to undo your own seals, come on,, this is itachi we are talking about.