Meanwhile, in Hong Kong, several hundred people who work in advertising started a five-day strike to show support for anti-government protests.
The move came as the world's two biggest economies have been striving to finalise a 'phase one' deal in their protracted trade war.
At one of Sunday's rallies -- a gathering to thank US lawmakers for their support -- protesters said they were determined to keep up the pressure on local authorities after the election victory.
Renewed calls to hit the streets came after Beijing and city leader Carrie Lam refused further political concessions despite a landslide victory for pro-democracy parties in local elections.
The Chinese Foreign Ministry's statements came just hours after Trump signed the Hong Kong Human Rights and Democracy Act of 2019 into law.
Some 2.94 million people voted out of 4.13 million citizens registered for the local election held on Sunday.
The run-up to Sunday's polls has seen a muting of major rallies and violent clashes between police and protesters, respite for a city battered by nearly six months of unprecedented political unrest.
Dozens of demonstrators have refused to leave the blockaded campus following intense clashes with police, though most have either escaped, voluntarily left or been arrested by officers.
There was a noticeable reduction in the police presence at Hong Kong Polytechnic University (PolyU), which entered the day fifth day of a stalemate.
China's foreign ministry in a statement said that they strongly urged their US counterpart to stop meddling in its internal affairs, take preventive measures and stop the bill from becoming a law.
The US lawmakers also approved a measure that would ban the sale of tear gas, rubber bullets and other equipment that have been used by security forces to suppress pro-democracy protests.
China condemned a decision by Beijing's High Court to overturn a ban on face masks worn by pro-democracy protesters.
The tweet from the fiercely nationalistic Global Times was live for little over half an hour before it vanished.
Authorities ordered schools and universities to close until next week, while hospitals deferred non-emergency operations.
With no end to the protests in sight, the beleaguered police force is appointing a group of prison guards as special constables.