With Microsoft Corp looking to buy short-video app TikTok's US operations, Trump said on Monday the US government should get a "substantial portion" of any deal price.
A police spokesman said the three men and a woman, all students, were suspected of being involved in an online group that pledged to use every means to fight for an independent Hong Kong.
"It marks the end of Hong Kong that the world knew before."
Originally valued at $46 billion, the estimate of CPEC projects is now $87b., and only a quarter of which have been completed.
The Chinese capital saw 158 new COVID-19 infections in the past week, with nearly all the cases linked to the Xinfadi Market in the southern district of Fengtai.
The return of COVID-19 in Beijing has shrouded the city, home to the headquarters of many big corporations, in uncertainty at a time China is trying to shake off the economic torpor of the virus.
The Beijing outbreak has already spread to the neighboring northeastern province of Liaoning.
Reuters has not seen the briefing paper, but it was described by people who had direct knowledge of its findings.
Beijing faces a wave of anti-China sentiment led by the United States in the aftermath of the pandemic and needs to be prepared in a worst-case scenario for armed confrontation.