Trump's comments come even as violent clashes erupted outside Hong Kong airport on Tuesday evening as riot police tried to disperse protesters as authorities suspended check-ins at the international airport.
Reports said police used pepper spray in scuffles with protesters at Hong Kong airport. At least two protesters were detained, reports said.
Several police vehicles were blocked by protesters, and riot police moved in, pushing some protesters back and using pepper spray at times.
The airport authority said in a statement that a public assembly had blocked passageways to the airport's restricted area, blocking passengers from proceeding to immigration.
In the second day of unrest at the airport, thousands of black-clad protesters jammed the terminal, chanting, singing and waving banners.
Scuffles broke out after an injured person was taken out of the main terminal by medics after he was held by a group of protesters. Some activists claimed he was an undercover mainland Chinese police officer.
Protesters also barricaded some passageways in the airport with luggage trolleys, metal barriers and other objects. At least two protesters were taken away by police.
The situation calmed down after a few hours without the violence worsening.