Washington DC - The US agency in charge of nuclear weapons is putting most of its workforce on unpaid leave, a top Republican lawmaker warned Friday, as a prolonged government shutdown bit further into already crippled public services.

With the standoff in Congress over federal spending in its 17th day and no breakthrough in sight, House Armed Services Committee Chairman Mike Rogers told reporters the National Nuclear Security Administration (NNSA) was about to run out of money.

"They will have to lay off 80% of their employees. These are not employees that you want to go home," he told reporters.

"They're managing and handling a very important strategic asset for us. They need to be at work and being paid."

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Rogers's committee later clarified that the employees would be furloughed – or placed on forced unpaid leave – rather than fired permanently.

The US has a stockpile of 5,177 nuclear warheads, with about 1,770 deployed, according to the global security nonprofit Bulletin of the Atomic Scientists.

The NNSA is responsible for designing, manufacturing, servicing, and securing the weapons. It has fewer than 2,000 federal employees who oversee some 60,000 contractors.

Energy Secretary Chris Wright told USA Today in an interview Thursday, touching on the effects of the shutdown on the NNSA.

"Starting next week, we're going to have to let go tens of thousands...of workers that are critical to our national security," Wright said, with the outlet reporting that staff at the agency had been told that furloughs could begin as soon as Friday.