Mass walkouts planned for later this week are "wrong" because the government is offering public sector workers a "good deal", David Cameron has claimed.
The prime minister's appeal at the Local Government Association conference in Birmingham comes just two days before up to 750,000 staff stage a one-day strike over their pensions.
"To those considering strike action, at a time when discussions are ongoing, I would say to you: these strikes are wrong – for you, for the people you serve, for the good of the country," he said.
"It's the changes we propose that are right."
Mr Cameron sought to counter "scare stories" about the government's proposals. Unions object to increases to their pension contributions, a switch in the indexing of their pensions from retail price index to consumer price index inflation and an increase in their retirement age to 66.
The prime minister said public service pension schemes would remain 'defined benefit', meaning the amount received in retirement will be guaranteed.
"Any suggestion otherwise is completely untrue," he insisted.
"And any suggestion that we are stripping workers of the benefits they have already accumulated is untrue too."
Mr Cameron argued that essential reform was being conducted in a way which is fair on both taxpayers and public sector workers.
He insisted the age when public sector employers can take their pension had to rise for everyone.
"I know some people say this change should only affect new entrants to the pension scheme.
"But I'm sorry, I just don't think that's right.
"It's not just the people who are joining the workforce now who are living longer.
We're all living longer – so we must all play our part in dealing with this problem."
Mr Cameron stressed it was a "fact" that "anyone with a public service career ahead of them who carries on contributing to their pension will be better off for doing so" and that "what you have earned you will keep".
"That's why I can look you in the eye and say public service pensions will remain among the very best - much better, indeed, than for many private sector workers."
Thousands of schools are expected to be affected by strikes from the National Union of Teachers (NUT) and the Association of Teachers and Lecturers (ATL).
Public sector staff, including those from the Public and Commercial Services (PCS) union and University and College Union (UCU), could be joined by the Unison union if the current round of talks prove unsatisfactory.
Unite general secretary Len McCluskey, commenting on Mr Cameron's speech, said: "Rather than congratulating councils for cutting services, David Cameron should direct his oft vaunted communication skills to ensuring the upcoming pensions talks are constructive and reach a fair settlement.
"The unions have never opposed reforms - but we want to be fully engaged in them, not learning of them via media. We will also never sign up to something that will impoverish people who have done the right thing by saving all their working life for their retirement."
Cabinet Office minister Francis Maude and chief secretary to the Treasury Danny Alexander said it was "extremely disappointing" that strikes were taking place while talks are ongoing.
But they did not offer compromise on the three key issues unions are concerned by.
"Public service pensions will still be among the very best, with a guaranteed pension which very few private sector staff now enjoy," the pair said in a statement after yesterday's talks.
"We are proposing they will be paid later because people live longer, and that public sector staff will pay more, for a fairer balance between what they pay and what other taxpayers pay."