Rapid advancements in China’s military capabilities pose increasing risks to American supremacy in outer space, the head of the United States military’s space wing said on Monday.

Nina Armagno, director of staff of the U.S. Space Force, said Beijing had made significant progress in developing military space technology, including in areas such as satellite communications and re-useable spacecraft, which allow countries to rapidly scale up their space programs.

“I think it’s entirely possible they could catch up and surpass us, absolutely,” Armagno said at an event in Sydney run by the Australian Strategic Policy Institute, a research organization partly funded by the U.S. and Australian governments. “The progress they’ve made has been stunning, stunningly fast.”

Historically lagging in a space race dominated by the United States and Russia, Beijing has made significant advances in recent years that have alarmed Washington and other Western nations.