NBA club owners and players representatives return to the negotiating table on Tuesday with time running out before the expiration of their current collective bargaining agreement on June 30.

"I think Tuesday is a very important day in these negotiations," said NBA commissioner David Stern. "I really think the time to have an optimistic or pessimistic view is at the close of the day on Tuesday."

Major areas of dispute remain despite five prior meetings this month, including a 4 1/2-hour bargaining session last Friday.

Should the sides not be able to reach a deal before the end of the month, there is a possibility of a lockout similar to the ongoing NFL stalemate with its owners and players, a shutdown set to reach its 100th day on Thursday.

"There is a very clear sense of urgency, but we are not sure between now and July 1 if we can make up the gulf that exists between the two sides," said Los Angeles Lakers standout Derek Fisher, president of the NBA Players Association.

Stern has said that while eight NBA clubs are hefty moneymakers, the other 22 teams lose money and many of them lose quite a lot of money. Players want to maintain the current system.

NBA team owners want a hard salary cap in place instead of the current system, which has loopholes and exceptions and does not keep owners from bidding against one another in boosting the payout for star players.

Current NBA rules gave the Cleveland Cavaliers a financial edge in offering LeBron James more money last July when he became a free agent but it was not enough to keep him from leaving to join the Miami Heat, helping them to this month's NBA finals, where the Heat lost to the Dallas Mavericks.

Owners want contract lengths reduced as well although they did roll back on a demand to end guaranteed contracts.

Owners want to trim about $2.1 billion spent on players last season by about $750 million and to reduce the current revenue split going to players, which is now guaranteed to be 57 percent.

Players have made a pitch to trim that percentage in talks but not enough to suit owners.

"We're very far apart still on some big items as well as some small items but not afraid of the July 1 deadline in terms of giving up," Fisher said. "We're still committed to trying to get something done (by) July 1."

Should they fail, the NBA could join the NFL in being shutdown and hoop fans would join their gridiron counterparts in worrying about whether or not next season would start on time or be played in full.

The NBA typically would not have training camps open until late September at the soonest with preseason games throughout October, some of them played in Europe in many years, ahead of a regular-season opener about Nov 1.