Nearly half of Americans have little or no confidence that they are financially prepared for retirement, a problem many of them intend to solve by working longer, according to a new survey.

The Employee Benefit Research Institute (EBRI) survey found that 10 percent of workers plan to retire between ages 66 and 69, and another 26 percent intend to put off retirement at least until age 70 — far more that planned to work that long when EBRI conducted its first retirement confidence survey in 1991.

Although many Americans are living longer and fewer are in physically demanding jobs, those plans to work longer may be unrealistic. The survey found that 47 percent of retirees left the workforce unexpectedly, largely because of disabilities, other health issues or problems at work.

At present, the largest group of workers leaves the workforce at age 62. That is when they initially qualify for reduced Social Security retirement benefits, which represents a smaller monthly amount for those who take it before hitting their full retirement age. Just 14 percent of the retirees captured in EBRI’s latest survey retired after age 65, and only one in four of them works for pay in retirement.

“The risk is that many workers as they get older cannot work for reasons beyond their control, including disability, ill health, and loss of a job and inability to get another,” said Mathew Greenwald of Mathew Greenwald and Associates, a public opinion firm that performed the survey.

Americans seem to have little choice but to plan to work as long as possible. One-third of workers say they or their spouse have not saved anything for retirement. And only 57 percent says they are actively saving for retirement.

The result is many are unprepared to stop working. Nearly three in five workers have assets, beyond their homes, of $25,000 or less. A third of those withdrew savings to pay for expenses in the last year, the survey found.

A big problem, researchers have said, is that too few workers are covered by retirement plans on the job. Those that are covered most frequently have a 401(k) or another defined contribution plan. But as many as one in four of people with those plans dip into them for non-retirement purposes, Matt Fellowes, chief executive of the benefits advisory firm HelloWallet told a Senate committee Tuesday.

Although Americans are aware that retirement requires substantial savings, they are unable to put away enough as they wrestle with expenses and burdensome debt.

“Many Americans have more immediate worries than saving for retirement,” said Jack VanDerhei, EBRI’s research director and co-author of the report.