The Hang Seng index fell 0.8pc to 26,222.40, while the China Enterprises Index dropped 0.9pc to 10,287.92.
Washington and Beijing labelled the two-day trade talks last week as "productive" and "constructive", with the US Trade Representative's office saying that high-level negotiations will take place in October, as previously planned.
However, investors' appetite for risk assets was curbed after Chinese officials unexpectedly cancelled a visit to farms in Montana and Nebraska.
Trade experts, executives and government officials in both countries said that even if the September and October talks produced an interim deal, the US-China trade war has hardened into a political and ideological battle that runs far deeper than tariffs and could take years to resolve.
Protests over the weekend piled pressure on shares listed on the island.
Hong Kong police fired tear gas on Sunday to break up pro-democracy protesters who trashed fittings at a railway station and shopping mall, the latest confrontation in more than three months of often violent unrest.
Around the region, MSCI's Asia ex-Japan stock index was weaker by 0.28pc.
The yuan was quoted at 7.1232 per US dollar at 08:14 GMT, 0.45pc weaker than the previous close of 7.0915.
The top gainers among H-shares were Guangdong Investment Ltd up 1.02pc, followed by Want Want China Holdings Ltd , gaining 0.82pc and China Telecom Corp Ltd, up by 0.56pc.
The three biggest H-shares percentage decliners were Sunac China Holdings Ltd, which was down 4.22pc, China Communications Construction Co Ltd, which fell 3.73pc and CITIC Securities Co Ltd, down by 3.71pc.
At close, China's A-shares were trading at a premium of 29.43pc over Hong Kong-listed H-shares.