The state pension age is set to "drift into the late 60s" across Europe, Justice Secretary Ken Clarke says.
He warns the default retirement age of 65 had been "unaffordable" as people continue to live longer (see the Pensions guide guide).
Chancellor George Osborne and Work and Pensions Secretary Iain Duncan Smith were probably "locked in discussions" over the pension age, he adds.
The coalition is examining how to raise the state pension age for men to 66 from 2016, nearly a decade earlier than the last Government was planning.
Ministers have also raised the possibility of extending the pension age to 70 and even older in the following decades.
The previous Labour government's policy was to raise the state pension age to 66 in 2024 and then incrementally to 68 by 2046.
Clarke, 70, says: "I'm sitting here, I'm a living advertisement, and I do appreciate I happen to be exceptionally lucky that I'm able to do a full-time job as I have. I know of many people that can't, of course.
"But a universal retirement benefit at the age we had it was unaffordable. Think of our children, think of our grandchildren who are going to have to pay for it when there are many fewer of them than there are these long-lived retired people we have now.
"The French have been so mad as to have riots in the street raising their age from 60 to 62, when our age is about in line with the normal, when you will find across Europe I think the retirement age will drift up into the late 60s.
"Whether on this occasion or not, I honestly don't know. I should think Iain and George are locked in discussions about that on the fringes of this conference."
Tory MP Mark Field, who will turn 46 tomorrow, adds: "I'm afraid people of my generation have got to recognise they're probably going to have to work now until the age of 70 or so.
"Clearly if people are in very difficult manual jobs that is more difficult, but I think the retirement age is going to have to go up quite radically."
Further reading/Key links
Boost income: Benefits, Pension Credit, State Pension Boosting
More on pensions: Pensions guide, Free, printed annuity guide