All it usually takes to borrow money from your 401(k) are a few clicks on a website, and a check will arrive a few days later.

That is why U.S. retirement industry leaders talk about the prospect of doing away with 401(k) loans before younger workers follow in the footsteps of previous generations and start using their retirement account like an ATM.

Workers who take out 401(k) loans risk not having enough saved for retirement because they miss out on growth while the money is borrowed.

Some may also reduce their contributions or stop them altogether, research shows.

Internal Revenue Service rules say you can borrow up to $50,000 or 50 percent of the account balance, whichever is greater.

This ability to cash out some portion of your retirement account balance is unique to 401(k) plans. You cannot borrow against an Individual Retirement Account or a pension, for instance.

The problem is with middle-aged workers, who are the heaviest loan users, according data from the Employee Benefit Research Institute. The overall average of loans has hovered between 18 and 20 percent for the last few years; about 27 percent of participants in their 40s had a loan balance in 2013, the last year of EBRI's data. Workers can take out money as withdrawals without penalty after age 59 1/2.

"New employees won't notice, but sure as heck the older ones would notice it," said EBRI Research Director Jack VanDerhei.

Among developed countries with private retirement systems, the United States is alone in allowing basically unrestricted access to cash without providing proof of a hardship, according to a recent study led by Brigitte Madrian, a professor at Harvard's Kennedy School of Government.

In fact, loans were used to entice workers dependent on pension plans to enroll in 401(k)s when they were introduced in 1981.