A staff report of the U.S. International Trade Commission says Nvidia Corp. (NVDA) illegally uses technology owned by Rambus Inc. (RMBS), and recommends a ban on U.S. imports of Nvidia's graphics chips.

Rambus, based in Los Altos, Calif., has alleged that Santa Clara, Calif.-based Nvidia uses its technology in its computer-based graphics chips. While the staff recommendation can be taken as an indication of the ITC's ultimate decision, there are times when the administrative judge will rule differently.

A trial on the case began on Tuesday and is ongoing. The original complaint was filed to the ITC by Rambus in November.

Nvidia declined to comment.

Rambus wasn't immediately available for comment.

Rambus shares fell 2.5% to $18.54, while Nvidia retreated 2.8% to $13.15.

-By Roger Cheng, Dow Jones Newswires; 212-416-2153; roger.cheng@dowjones.com