The Swiss third seed went from impressive to battling as he claimed a 6-3 6-4 3-6 7-6 (7-1) victory over Brazil's Bellucci.
Wawrinka - the Australian Open champion - had starred on Arthur Ashe Stadium during the first two sets thanks to his shot-making and aggressive approach.
He hit 25 winners in the opening two sets against Bellucci, who had won the only previous encounter between the pair on clay in 2009.
But, perhaps losing concentration with the finish line in sight, Wawrinka began to falter and Bellucci capitalised.
Wawrinka committed 16 unforced errors in the third set and fell behind a break early in the fourth.
He got back on serve before squandering two match points in the 10th game.
Wawrinka made the perfect start to the tie-break and that would be enough to claim the win and set up a meeting with Slovenian Blaz Kavcic.
With 51 winners and 43 unforced errors, Wawrinka's final numbers looked impressive, but he will want a repeat of what he produced in the first two sets.