Italy's largest trade union, the CGIL, says it will hold a general strike over plans to reform employment job/law/ target=_blank class=infotextkey>laws.
After weeks of talks, Prime Minister Mario Monti said he wanted the changes, making it easier for companies to sack staff, approved by the end of the week.
Maurizio Landini, a CGIL leader, said its members were "ready for anything" if Mr Monti pressed on with the changes.
The reforms also offer companies fresh incentives to take on new staff.
The government hopes the changes will help create more jobs and boost competitiveness, while protecting Italy from the eurozone debt crisis.
Mr Monti, who heads a government of technocrats, has already introduced a series of wide-ranging reforms.
Mr Landini - who is a leader of the influential metalworker's union, a part of the CGIL - said the new changes only increase the uncertainties for workers.
Support from Brussels
He said they would be opposed with all forms of "democratic protest" across the country.
The CGIL will announce more details of its strike plans later on Wednesday.
But the reforms are supported by the European Union.
Laszlo Andor, the European Employment Commissioner, said it was good that the Italian government has "invested so much time" in negotiations with the trade unions.
"Mr Monti is going to revitalise the labour market, which meets our goal of creating a more dynamic market, and it's a direction worthy of support," said Mr Andor.
The reforms went further than expected by weakening protections against dismissal（解雇，免职） not only for new workers, as expected, but also for millions of people already in jobs.
They are aimed at changing Article 18 of the employment code, on compulsory reinstatement of unjob/law/ target=_blank class=infotextkey>lawfully dismissed workers, which was drawn up in its current form 40 years ago when the unions were at the height of their powers.
The changes will be presented to parliament after fine-tuning later in the week.