Elections for Hong Kong's legislature will likely be deferred for a second year to September 2022 as Beijing plans a major overhaul of the city's electoral system, dealing a severe blow to remaining democratic hopes in the global financial hub.

The delay, which South China Morning Post and other local media reported on Friday, citing unnamed sources, would be in line with a new effort by Beijing to ensure "patriots" are in charge of all public institutions in the former British colony.

Zhang Yesui, a spokesperson for the National People's Congress, said on Thursday it had the constitutional power to "improve" Hong Kong's system and a draft decision would be discussed during the annual...