The Argentine, who has dropped just one set in his last nine matches on the surface which included his run to the title last week in Estoril, proved too strong for Croat Ancic.
"I felt a bit tired during my first two matches in Rome, but now I'm getting stronger, and starting to feel more confident," said the world number three who will play either top seed Roger Federer or Spanish qualifier Nicolas Almagro in the last four.
