By Simon Evans

NEW ORLEANS (Reuters) - NFL commissioner Roger Goodell has warned that a deal with the players' union over a new collective bargaining agreement will be "more complicated" to reach if it is not struck before March.

The current deal, which governs a raft of financial and contractual issues, expires in March and Goodell told a fan forum at the Louisiana Superdome on Wednesday that a sufficient window of time existed between now and March to strike a deal.

"We have plenty of time to get this done but we do have a window, we need to get this done sooner rather than later. Come March it becomes a lot more complicated," Goodell said when asked by a fan about talk of a work stoppage in 2011.

"Our focus is to get down to some serious negotiations, get some issues resolved and keep playing football - that's what we all want to do."

If a new agreement is not in place by March there would be confusion of having no salary cap in place and the uncertainty could have a commercial impact on the league.

The NFL season opens Thursday with the New Orleans Saints, last season's Super Bowl champions, hosting the Minnesota Vikings in a rematch of January's NFC Championship game.

One of the sticking points between the league and the players is the issue of rookie compensation.

The St. Louis Rams signed rookie quarterback Sam Bradford to a record deal during the off-season tying him to a six-year $78-million contract with $50 million guaranteed.

"I am a firm believer that we need to change our rookie compensation. The money should be going to the veterans that have earned it on this field right here," said. Goodell.

"We need to do more for our retired players, I think we need to do more for investments in our game so we can continue to make the game better and bigger and I think we need to improve on the quality of what we do, we always need to focus on player health and safety and to focus on the integrity of the game and that (means) improving on our drug testing program."

(Editing by Frank Pingue)