In a statement posted on the US Treasury Department website, the Biden administration said most investments in companies "whose name closely matches, but does not exactly match, the name of a Communist Chinese military company" would be allowed until May 27.
The order does not authorize securities transactions with subsidiaries of banned Chinese military companies, it added.
In November, former US President Donald Trump's administration moved to prohibit US investments in Chinese companies that Washington said were owned or controlled by the Chinese military in an effort to ramp up pressure on Beijing following the Nov. 3, 2020 US presidential election.
The order prohibited US investors from buying securities in such companies and was thought to impact some of China's biggest companies, although some have denied military links.
Beijing has said the United States lacks evidence and described the ban as wanton oppression of its companies.