Both sides in the NFL's labor talks are trying to spread the word by putting their positions in writing, and everyone's getting in on the act _ from Hall of Fame players Jack Youngblood and Bruce Smith, to Commissioner Roger Goodell, to mayors of league cities.

In a letter obtained by The Associated Press on Tuesday, Youngblood and Smith asked NFL owners to promise not to lock out players even if a new collective bargaining agreement isn't reached by the time the current one expires at the end of the day March 3.

Youngblood was elected to the Pro Football Hall of Fame in 2001, Smith in 2009. Their letter was addressed to "Owners of the National Football League" and sent Jan. 31 to Goodell at league headquarters in New York.

"As former players, it is crystal clear that the vast popularity and financial success of football means that a lock out cannot be in the interest of anybody involved, particularly the fans who support the game," Youngblood and Smith wrote. "We understand the need for both sides to create pressure, but also know that at times it is important to decrease tenor and tone in order for the right deal to be made in a non-emotional atmosphere."

They noted that the players' union already "pledged to not strike."

"By making the parallel commitment," they wrote, "the owners would create the breathing room for a deal to be struck."

That exact wording also was used in a Feb. 7 letter from Kansas City, Mo., Mayor Mark Funkhouser to Clark Hunt, the owner and chief executive officer of that city's NFL team, the Chiefs. Indeed, Funkhouser's two-paragraph letter to Hunt uses phrases throughout that echo the letter to Goodell from Youngblood and Smith.

Mayors or city officials from at least five sites of NFL teams have written letters to the league or a club official to argue against a lockout.

Goodell, meanwhile, indicated in an op-ed piece that the 2011 regular season could be in jeopardy if the league and union don't start "serious negotiations" toward a new CBA soon.

"The hard work to secure the next NFL season must now accelerate in earnest," Goodell wrote in the piece, which has been run by more than 30 newspapers or websites since last week and was posted Tuesday on NFLlabor.com.

He said he "cannot emphasize enough the importance of reaching agreement by" the expiration of the old CBA.

Goodell also said owners need more money to offset "costs of financing, building, maintaining and operating stadiums." He added: "We need new stadiums in Los Angeles, Minneapolis, San Francisco, Oakland and San Diego."

The biggest issue separating the sides is how to divide about $9 billion in annual revenues; under the old deal, the owners receive $1 billion off the top, and they want to increase that to $2 billion before players get their share.

Among the other significant points in negotiations: the owners' push to expand the regular season from 16 games to 18 while reducing the preseason by two games; a rookie wage scale; and benefits for retired players.

The NFL and union went more than two months without holding any formal bargaining sessions, until a meeting Feb. 5, the day before the Super Bowl. The sides met again once last week but called off a second meeting that had been scheduled for the following day.

The most recent deal was signed in 2006, but owners exercised an opt-out clause in 2008.

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Associated Press Writer Bill Draper in Kansas City, Mo., contributed to this report.