A "smoothly functioning" system of commerce in Hong Kong is "fundamentally important" to the business interests of its members in the mainland, a US business organization said.

"It is without question that smoothly functioning Hong Kong commerce is fundamentally important to our members' business interests and an important validator of the 'one country, two systems' approach," Timothy Stratford, chairman of the American Chamber of Commerce in China (AmCham China), said in an interview with the South China Morning Post.

"Faithful implementation of this approach helps Hong Kong maintain its reputation as an attractive destination for foreign investment," he added.

Last year, Hong Kong attracted $116 billion in foreign direct investment, ranking third worldwide, according to a UN report released on June 12.

Earlier this week, Yang Guang, a spokesman for the Hong Kong and Macao Affairs Office of the State Council, said at a news conference that violent clashes between the police and protesters have affected the city's economy, harming tourism and retail sales.

"The political protests that began in June have had a detrimental effect on Hong Kong's economy and even dampened overseas investors' confidence in Hong Kong," Yang said.

Hong Kong's economic output in the second quarter increased 0.6 percent year-on-year, according to its Census and Statistics Department. Retail sales declined 6.7 percent year-on-year in June, falling for the fifth consecutive month.

The city's Chief Executive Carrie Lam Cheng Yuet-ngor warned on Friday that Asia's financial center is bracing for an "economic tsunami" never before seen, after meeting with 33 representatives from the business community.