CANBERRA, Australia (AP) — Australia's critical infrastructure including electricity grids, water supplies and hospitals could not have been adequately safeguarded if Chinese-owned telecommunications giants Huawei and ZTE Corp. were allowed to help roll out the nation's 5G network, a spy chief said.

Mike Burgess, director-general of the Australian Signals Directorate, said his cyber experts had backed the government's decision in August to bar the two Chinese companies that he described as "high-risk vendors." It was the first time the secretive agency had disclosed such information.

"My advic...