Quarterback Dak Prescott has been franchise tagged by the Dallas Cowboys.

Prescott, who usurped Tony Romo as the Cowboys' starter after being drafted in the fourth round in 2016, was given the exclusive tag on Monday as the NFL's legal tampering period for free agents got under way.

He will earn the average of the top five salaries at his position in a one-year pact, with the tag expected to be worth $33million.

With his services secured for 2020, the team and player will continue negotiations over a long-term deal, which as yet have not ended in an agreement.

After an offseason of speculation, the development means Cowboys wide receiver Amari Cooper will hit free agency.

The new collective bargaining agreement that was approved over the weekend ensured teams were only allowed to use one of the franchise and transition tags this offseason.

Prescott threw for 30 touchdowns and had 11 interceptions last year, racking up a career-high 4,902 yards.

The 26-year-old has led the Cowboys to two NFC East titles but they are yet to go beyond the divisional round of the playoffs.

Prescott will be playing under a new head coach next season after Mike McCarthy replaced Jason Garrett, who lost his job after nine-and-a-half years in the role.