The talks come weeks ahead of the US presidential election and amid tensions between the US and China over the virus, trade, technology, Hong Kong, Taiwan and human rights.
Reports suggest the talks could now continue for the rest of October, but British officials are stressing the need for clarity on whether a deal is feasible by the summit.
According to official figures, there were 12,872 new cases on Saturday, while a further 49 people have died within 28 days of testing positive for COVID-19.