PHOENIX (AP) ― Concerned with how it will be officiated, NFL owners delayed voting Tuesday on a rule change that would ban offensive players from using the crown of their helmets against defenders in the open field.

After approving two other rule changes to enhance player safety, they stalled on the more contentious issue. NFL senior vice president of football operations Ray Anderson said the owners plan to vote on it Wednesday before the meetings end.

The owners outlawed peel-back blocks anywhere on the field; previously, they were illegal only inside the tackle box. A player makes a peel-back block when he is moving toward his goal line, approaches an opponent from behind or the side, and makes contact below the waist.

The penalty will be 15 yards.

“... really under no circumstances will you be permitted to block low below the waist when you’re blocking back towards your own end line,” said Rams coach Jeff Fisher, co-chairman of the competition committee.

Also banned is overloading a formation while attempting to block a field goal or extra point. Defensive teams can now have only six or less players on each side of the snapper at the line of scrimmage. Players not on the line can’t push teammates on the line into blockers, either.

The alignment violation is a 5-yard penalty. The pushing penalty is 15 yards for unnecessary roughness.