The Clippers are missing a number of key players and have been heavily linked with fee agent Jackson.
"It's not done yet," Rivers told reporters after his team's win over the Philadelphia 76ers on Tuesday night.
"Nothing's done in our league until it's done, as you know. I just think he's a veteran.
"We need him in a pinch, and we need him, like, now. That's a guy you can bring in, and hopefully he can give you something right away."
Jackson has not played an NBA game since being released by the San Antonio Spurs shortly before last season's playoffs.