As they struggle to save for retirement, a growing number of middle-class Americans plan to postpone their golden years until they are in their 80's.

Nearly one-third, or 30%, now plan to work until they are 80 or older -- up from 25% a year ago, according to a Wells Fargo survey of 1,000 adults with income less than $100,000.

"It is so tough for Americans to save for retirement that the answer seems to be to work longer," said Joe Ready, director of Wells Fargo Institutional Retirement and Trust.

Overall, 70% of respondents plan to work during retirement, many of whom plan to do so because they simply won't be able to afford to retire full time.

But working well into your 70's, 80's or even 90's, isn't always realistic, said Ready. Nearly three-quarters of those who plan to work into their 80's say their employer won't want them working when they're that old, for example. Other roadblocks, like health issues, could arise as well.

Those who are unable to work as long as they intend could therefore face a very grim reality. In fact, more than one-third of Americans could wind up living at or near poverty in retirement, the survey found.