It has been reported that the two ships in question were the USS Green Bay and USS Lake Erie, which were set for visits in the semi-autonomous city in late August and September.
— Barbara Starr (@barbarastarrcnn) August 13, 2019
Speaking to Reuters, a source familiar with the matter indicated that a specific reason was not given.
However, the denial is not unprecedented, as China previously denied a similar request in September 2018 from the US Navy's USS Wasp F-35 carrier. At the time, the rejected port call came amid trade tensions between the US and China and Beijing's decision to recall an admiral from the International Seapower Symposium.
The latest port denial comes as protests in Hong Kong continue to cause turmoil in the city and as demonstrators managed to paralyze the Hong Kong airport for a second day. Earlier on in the day, US President Donald Trump fired off a tweet, revealing that intelligence sources had indicated Beijing was "moving troops to the border with Hong Kong."
Protests in the city initially began as a result of outrage over a bill that would have allowed extradition to mainland China; however, that measure has since been withdrawn.