The In Da Club star, real name Curtis Jackson, was recently criticised by Nas on the track Queens Get the Money, from his self-titled 2008 album.
But 50 Cent has refused to be drawn into a lyrical battle with Nas - claiming he hasn't even heard the song because it's too far below his radar.
He tells XXL magazine, "Nas is cold as ice. Nas is the block of ice that sunk the Titanic... I didn't even hear his record. I didn't even hear what you talking about...
"I really don't want to talk about Nas. I think he's at one of those points to where his career's finished, to be honest.
"He's had some great moments and made good music in the past, but he no longer has the interest of the general public or myself."
Source: WENN