WASHINGTON, Nov 28 (Reuters) - The United States backs the right of people to peacefully protest in China, Washington said on Monday as protesters in multiple Chinese cities have demonstrated against heavy COVID-19 measures in recent days.Chinese police on Monday tightened security at the sites of weekend protests in Shanghai and Beijing, after crowds there and in other Chinese cities and dozens of university campuses made a show of civil disobedience unprecedented since leader Xi Jinping assumed power a decade ago."We think it's going to be very difficult for the People's Republic of China to be able to contain this virus through their zero-COVID strategy," the spokesperson said, adding that the United States was focused on "what works" to combat the virus, including by enhancing vaccination rates.Beijing and Washington have dealt with the spread of the coronavirus pandemic in vastly different ways, a split that has reshaped the contest between the world's two leading economies.The backlash against COVID curbs is a setback for China's efforts to eradicate the virus, which is infecting record numbers after swathes of the population sacrificed income, mobility and mental health to prevent it from spreading."