The Italian Serie A may not begin on time unless a dispute over players' rights is resolved before the end of the month.
The Italian Players Union (AIC) said the league has still not signed an agreement reached with the players last year after intense negotiations, after criticising clubs for trying to force players to move in the last year of their contracts.
"The collective contract must be signed and it needs to be done before the start of the championship," Damiano Tommasi, the new head of the AIC, said. "It's difficult for the players to not go on to the pitch, but it's necessary to have this in black and white.
"I've visited 90% of the teams' pre-season training camps and there is unity among the players."
Strikes were called off at the last minute at the end of last year and a new deal is awaiting the signature of the league.
"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," Tommasi added. "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 underway."