James Gandolfini plays mafia boss Tony Soprano

The network told 300 staff involved with the show on Thursday that they need not report for work on 24 March, the day the fifth series of the show was supposed to begin filming.

They said they were unsure whether Gandolfini would show up for work.

The postponement is indefinite following the outbreak of a legal battle between the network and Gandolfini, who plays mafia boss Tony Soprano in the show.

Gandolfini sued the network last week in a bid to increase his pay.

In his suit Gandolfini said he wanted double the current $400,000 (�256,000) per episode. He is claiming he is under no obligation to return to the show's fifth series.

He also said the show's producers did not tell him in a timely manner that he would be needed for a fifth series.

$100m countersuit

"It looks pretty grim," HBO's lawyer Bert Fields said. "HBO is not going to pay him what he is demanding and right now he is saying he will not honour the contract."

HBO then filed a countersuit, warning him that he could be liable for $100m (�64.2m) if he walks out on the show.

The last offer made to Gandolfini for the 13-episode fifth season was for $11m (�6.8m), part of which was to be paid in profit participation.

But Gandolfini was reported to be asking for as much as $27m (�16.8m), and $16.7m (�10.4m) for a sixth season, should one be ordered.

The show broke records for cable shows last year when it attracted 13.4m viewers for its first episode.

HBO had previously said it accommodated Gandolfini's schedule when he wanted to do movies, and that it was tolerant of the personal problems he had experienced while starring in the show.

Gandolfini has appeared in films such as The Mexican, starring Brad Pitt and Julia Roberts, and the Coen brothers' The Man Who Wasn't There.

"Let HBO say whatever they want to say," said Gandolfini's spokesman, Dan Klores.

"It should be beneath them to treat one of their biggest stars, moneymakers and friends like this."