They flew US flags and banners reading, “President Trump, please save Hong Kong” and “Make Hong Kong great again”.
The protests, now in their 14th straight week, have continued despite concessions by Hong Kong’s leadership.
China has consistently warned other countries not to interfere in the former British colony.
It says the situation in Hong Kong is purely its own internal affair.
Sunday’s crowd chanted pleas for the US to “liberate” Hong Kong from China.
Protesters sang the US national anthem, The Star-Spangled Banner, and a new rallying cry of “five demands, not one less” – after one of their long-standing conditions for ending demonstrations was met earlier this week.
On Saturday, some protesters attempted to gain access to the international airport, the site of previous demonstrations. But police only allowed airline passengers with a ticket to board trains and buses bound for the terminal.
What do protesters want?
The protests first erupted over a controversial extradition law which would have allowed Hong Kongers to be extradited to mainland China – where a different legal system applies.
Mass protests involving hundreds of thousands of people demanded that the plan be abandoned. It was initially suspended in June, and then finally dropped earlier this week.
In the meantime, the protesters’ demands had spiralled into a much wider set of reforms.
Four of their demands remain unmet:
- Withdrawal of the “riot” description used about the protests
- Amnesty for all arrested protesters
- An independent inquiry into alleged police brutality
- Universal suffrage for the elections of the chief executive and Legislative Council, Hong Kong’s parliament
Some also want Hong Kong’s political leader, Carrie Lam, to resign, accusing her of being controlled by the mainland government in Beijing.
Is the US likely to get involved?
The appeal for US intervention comes despite President Donald Trump’s characterisation of Chinese leader Xi Jinping as “a great leader who very much has the respect of his people”.
“I have zero doubt that if President Xi wants to quickly and humanely solve the Hong Kong problem, he can do it,” Mr Trump tweeted in mid-August.
On Saturday, US Secretary of Defense Mark Esper said China should show “restraint”.
Instead of a crackdown, he urged Chinese authorities to “to sit down and talk with the protesters and resolve the differences.”
For its part, China has not only warned foreign powers not to interfere, but has outright accused the US and Britain of encouraging the protests.
The US State Department has issued a travel advisory for Americans visiting Hong Kong, warning that US citizens and diplomatic staff “have been subject to a People’s Republic of China propaganda campaign falsely accusing the United States of fomenting unrest in Hong Kong.”