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Planning to work longer is a popular escape hatch for Americans who feel they've saved too little to support themselves in old age. About 27% of workers intend to work in retirement because they need to supplement their income, according to a new CNBC and SurveyMonkey survey. They polled 6,657 U.S. adults in early August, including 2,603 who are retired and 4,054 who are working full time or part time, are self-employed or who own a business. While working longer is among the best ways to shore up one's nest egg, the plan may backfire, according to retirement experts.

Workers may not be able to work into their late 60s, early 70s or later due to an unexpected health complication or a layoff, for example. "It sounds great on paper," said Philip Chao, a certified financial planner and founder of Experiential Wealth, based in Cabin John, Maryland. "But reality could be very different." If workers lose those wages, they'd have to figure out another way to make their retirement savings last.

Workers often retire earlier than planned

A nonexistent 'escape valve'

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