Britain is facing the threat of mass walkouts by public sector workers after the biggest unions announced strike ballots over pensions.
Unison, Unite, the GMB and the Fire Brigades' Union will consult members about co-ordinated industrial action starting in November.
Unison's leader Dave Prentis told the TUC's annual conference the strikes would involve the "fight of our lives".
But the government said widespread action would leave the public "angry".
Ministers are seeking increases in pension contributions from next April, while millions of workers continue to face a pay freeze.
The coalition argues that rises in payments are fair and will make schemes sustainable despite an ageing population.
'This is it'
Proposing a motion backing mass strikes to the TUC conference, Mr Prentis revealed he was giving 9,000 employers formal notice that his union's 1.1 million members would be balloted.
He said: "We've had enough. We've been patient, co-operative and we must say enough is enough."
"If we don't say it now, they [the government] will be back for more and more and more again.
"We will engage with them... but if they impose change by diktat, we will take industrial action."
He added: "It's the fight of our lives. I know it's an over-used cliché, but make no mistake, this is it."
Mr Prentis, who won a standing ovation from the 300 TUC delegates, was followed by series of other union representatives, who backed the action.
Gail Cartmail, assistant general secretary of Unite, said: "When the coalition came to power we knew we faced the fight of our lives. We knew they would seek to weaken and divide us.
"While we will never walk away from talks, neither can we sit on our hands. We will support days of action and tactical selective action."
The GMB's Brian Strutton said: "We're not talking about a day out and a bit of a protest. We're talking about something that's long and hard and dirty as well, because this is going to require days of action running through the winter, through into next year, following the government's legislative programme right into the summer."
Public and Commercial Services Union general secretary Mark Serwotka also supported action by "millions" of people, adding: "Marching together we can win."
Continue reading - BBC - Unions to ballot on nationwide pension strikes