Board Thread:Naruto Discussions/@comment-25358381-20140903032737/@comment-24860855-20140905030403

he didn't stop it. amaterasu burns what in the users sight until that object or person is completely engulfed and burned into nothing. Itachi used it on sasuke's fire ball jutsu, once all the flames from sasuke's jutsu were extinguished it had nothing more to burn thus ending the amaterasu.