America's nuclear force still uses floppy disks designed in the 1970s to coordinate some of its functions, according to a watchdog report released Wednesday.

The report by the Government Accountability Office points to a number of worryingly outdated "legacy systems" still in use across the US government that are in desperate need of upgrading.

A Pentagon command and control system that "coordinates the operational functions of the United States' nuclear forces, such as intercontinental ballistic missiles, nuclear bombers, and tanker support aircrafts," runs on an IBM Series/1 computer and uses 8-inch floppy disks, the report says.

That type of computer debuted in 1976, when Gerald Ford was in the White House.

"This system remains in use because, in short, it still works," Pentagon spokeswoman Lt. Col. Valerie Henderson told AFP.

"However, to address obsolescence concerns, the floppy drives are scheduled to be replaced with Secure Digital devices by the end of 2017," she added.

"Modernization across the entire Nuclear Command, Control, and Communications (NC3) enterprise remains ongoing."

According to the GAO report, the Pentagon is planning to fully replace the system by the end of 2020.

The GAO said the federal government is spending a lot more on "operations and maintenance" of its computer systems than it is on "development, modernization and enhancement."

Last year, for instance, the government spent $61.2 billion on operations and maintenance, compared to $19.2 billion in the other category.

The report also found that the Treasury Department uses "assembly language code," which was initially designed in the 1950s.

The Office of Management and Budget has started an initiative to replace the legacy IT systems, "but until this policy is finalized and fully executed, the government runs the risk of maintaining systems that have outlived their effectiveness," the report states.