Joshua Wong said it was crucial Hong Kong was factored into negotiations between Beijing and Washington.

Hong Kong activist Joshua Wong urged US President Donald Trump on Friday to include a "human rights clause" in any trade agreement with China, and sought Washington's backing for the city's democracy movement.

The 22-year-old called on American politicians to pass a bill expressing support for the pro-democracy campaign during a speaking engagement in New York, a few hours after arriving in the United States.

"It's significant to add a human rights clause in the trade negotiations and put Hong Kong protests under the agenda of the trade negotiations," Wong told AFP afterwards.

The world's two biggest economies have been locked in a bitter trade war for the past year, resulting in tit-for-tat tariffs on hundreds of billions of dollars in two-way trade.

Trade talks between Beijing and Washington are scheduled for October.

Wong said it was crucial Hong Kong was factored into the negotiations, saying it faced the threat of emergency laws "similar to martial law" and feared that China would send troops to the semi-autonomous region.

"If China has no intention to safeguard Hong Kong's economic freedom and open business it will also affect and damage the world economy," he said.

Wong arrived in the US after visiting Germany as he seeks global support for Hong Kong's widening pro-democracy protests that have crippled parts of the Asian financial hub in recent months, including its airport.

Millions have taken to Hong Kong's streets over the last 14 weeks in the biggest challenge to China's rule since the city's handover from Britain in 1997.

"Year of discontent"

Beijing summoned the German ambassador this week after Wong, one of the most prominent faces in the city's leaderless pro-democracy demonstrations, met Germany's foreign minister.

Wong is due to attend a Tuesday congressional hearing in Washington on the Hong Kong Human Rights and Democracy Act of 2019.

He will meet Republican Senator Marco Rubio, a vocal critic of China, who introduced the bill in June, but it's not clear if he will meet anyone from Trump's administration yet.

Wong urged Congress to pass the legislation, which could undermine Hong Kong's special US trade privileges by mandating regular checks on whether authorities were respecting the Basic Law that underpins the city's semi-autonomous status.

Hong Kong protesters have been increasingly calling for help from the US in recent weeks. On Sunday, thousands of demonstrators, some waving American flags, marched outside the US consulate in Hong Kong.

China has regularly accused "external forces," notably the United States, of being behind the unrest in Hong Kong, an accusation foreign countries deny.

Wong told around 200 students at New York's Columbia University the purpose of his US visit was to put Hong Kong "under the global spotlight."

"The summer of discontent is becoming the year of discontent," he said, indicating that activists would not back down until they are guaranteed free and fair elections -- a promise enshrined in the handover agreement between Britain and China.