NEW YORK (Reuters) - NFL commissioner Roger Goodell tried to reassure fans about the 2011 football season by saying in an open letter Monday that an agreement would be reached on a new collective bargaining agreement with the players union.

"Many fans have been asking me where we stand on signing a new collective bargaining agreement with the player's union. Let me update you and be clear at the outset," Goodell said in the letter posted on the league website (www.nfl.com).

"I know we can and will reach an agreement."

"NFL players deserve to be paid well," he said. "Unfortunately, economic realities are forcing everyone to make tough choices and the NFL is no different."

The commissioner said that besides the economic split of the revenue pie, key issues included extending the regular season from 16 to 18 games and setting a rookie salary cap.

"Fans tell us they don't like the quality of the preseason games, and we're listening," Goodell said about the current schedule that includes four preseason games.

"An enhanced season of 18 regular season and two preseason games would not add a single game for the players collectively, but would give fans more meaningful, high-quality football."

Players have expressed concern about increased injury risks of adding two regular season games to the schedule.

"Our emphasis on player health and safety is absolutely essential to the future of our game," Goodell said.

Getting a handle on rookie salaries was critical, he said.

"We must ensure the health of the league. That includes a new system that properly compensates proven veterans and retired players by shifting some of the outrageous sums paid to many unproven rookies," Goodell said.

"In 2009, NFL clubs contracted $1.2 billion to 256 drafted rookies with $585 million guaranteed before they had stepped on an NFL field.

"All we're asking for is a return to common sense in paying our rookies."

(Reporting by Larry Fine in New York, editing by Steve Ginsburg)