Nearly half of the nation's small-business owners are putting retirement plans on hold, fearing unexpected costs could deplete their savings, according to a recent survey by Wells Fargo.

Among 600 small-business owners polled by Gallup, rising medical costs was cited as the biggest risk to retirement savings. Roughly half of the respondents said they're worried about not being able to afford treatment for an unexpected illness or accident. As a result, many are delaying retirement plans and expect to keep working later in life, the survey found.  

"An increasing number of business owners who wish to retire are finding it difficult," Rebecca Macieira-Kaufmann, the head of Wells Fargo’s small-business segment, said in a statement. She said it was important for small-business owners to plan ahead for their retirement years, even if they don't foresee stopping work completely.