Dallas Cowboys quarterback Tony Romo has expressed his belief that the quality of his side's offensive line could extend his career.

The NFC East side are widely regarded to have the best line in the NFL as they provided solid protection for Romo last season, and also helped former running back DeMarco Murray become the leading rusher in the league in 2014.

The 35-year-old has refused to rule out playing beyond the age of 40 because of his belief in the players around him on the roster.

"When you have a good offensive line like we do, the thought definitely crosses your mind to ensure you do everything possible to play longer than maybe what you had envisioned," Romo told reporters.

"We'll reassess that in a few years. My wife will tell you, I'm talking a little more long term than I maybe had been.

"I just think the way this team has been built over the last three or four years has been from the inside out and you're seeing the benefits of that. We're still going. This wasn't a one-year, two - we're building this for the next five, six, seven years to sustain."

Romo threw for 3,705 yards and 34 touchdowns to nine interceptions in the 2014 season.