The Italian Players Union (AIC) said the Serie A league has still not signed an agreement reached with the players last year after intense negotiations, during which strikes were twice narrowly averted.
"The collective contract must be signed and it needs to be done before the start of the championship," said Damiano Tommasi, the new head of the AIC, in a television interview.
"It's difficult for the players to not go on to the pitch, but it's necessary to have this in black and white," added Tommasi, a former Roma and Italy midfielder who played at the 2002 World Cup.
"I've visited 90 percent of the teams' pre-season training camps and there is unity among the players."
An old collective agreement expired at the end of the 2009/10 season and talks for its renewal dragged on for the whole of last season.
The union was especially unhappy about clubs trying to force players to move in the last year of their contracts.
The matter came to a head in September and December when strikes were called off at the last minute, in the latter case with only two days to spare.
A last-minute deal meant all players with first-team contracts would be allowed to train with the main squad while rules to avoid discrimination were agreed for unwanted players who are put up for sale.
The AIC said it had signed the deal then but was still waiting for the league to add its signature.
"I keep hearing them say that there what we're nearly there, but that little bit that is missing on the League's part never arrives," said Tommasi.
"Last season, we decided not to stop the championship while it was still in progress but if we don't arrive at a conclusion this time, it will not get under way."
