Rams running back Steven Jackson has said this off-season that he wants a contract extension, and as of this afternoon he officially became a training camp holdout.

The St. Louis Post-Dispatch reports that Jackson’s agent, Eugene Parker, engaged in late-night negotiations with the team in an effort to finish up a contract extension, but so far they have not reached a deal.

Rams coach Scott Linehan said he considers getting Jackson extended a priority.

“I know within the last couple days there has been dialogue,” Linehan said. “Our hope is that will be done pretty soon.”

The 25-year-old Jackson is coming off his third straight 1,000-yard season, although he was hampered by injuries and significantly less productive in 2007 than he was in 2006.

Rams rookie wide receiver Donnie Avery is also absent from training camp. Avery, the Rams’ second-round pick, is expected to sign a contract soon.