Updated

By Julian Linden

NEW YORK (Reuters) - The NFL has refused to concede defeat in its bitter labor dispute with its players, announcing on Monday it will appeal a court ruling ordering the league to lift its lockout.

The players claimed an early victory when Minnesota District Judge Susan Nelson agreed to grant their request for an injunction and force the league to immediately reopen for business.

But the NFL, which imposed the lockout six weeks ago when protracted talks between the team owners and players' union collapsed, said they were not giving up without a fight.

"We will promptly seek a stay from Judge Nelson pending an expedited appeal to the Eighth Circuit Court of Appeals" the NFL said in a statement. "We believe that federal law bars injunctions in labor disputes. We are confident that the Eighth Circuit will agree."

If the Eighth Circuit Court agrees to hear the league's appeal and issues a stay on Nelson's ruling, the case would be expected to drag on for months, possibly threatening to disrupt the start of the 2011 season, scheduled for early September.

The owners and players are in a disagreement over a range of issues centered around how to carve up more than $9 billion in annual revenues.

Under the current agreement, owners received a guaranteed $1 billion while the rest was split, with the players getting around 60 percent and the owners 40 percent.

The league and owners want to increase their automatic cut by another $1 billion, arguing that operational costs had risen since the last deal was struck five years ago, but the players wanted to maintain the status quo, claiming the owners had failed to provide them with enough financial evidence to prove they needed a bigger slice of the profits.

Both sides have been heavily criticized by sections of the American public at a time when many families are struggling to make ends meet.

Judge Nelson told both sides they would be better off returning to the negotiating table to sort out their differences themselves and the NFL said they still believe that is the best solution for everyone.

"We also believe that this dispute will inevitably end with a collective bargaining agreement, which would be in the best interests of players, clubs and fans," the NFL said in their statement. "We can reach a fair agreement only if we continue negotiations toward that goal."

(Editing by Frank Pingue)