The United States called on China Sunday to release all prisoners still detained for their involvement in pro-democracy demonstrations 23 years ago, DPA reported.
The move came on the anniversary of the crackdown that ended the demonstrations centred around the capital's Tienanmen Square.
The statement released by US Department of State Deputy Spokesman Mark Toner also called on Beijing to "provide a full public accounting of those killed, detained or missing; and to end the continued harassment of demonstration participants and their families."
"We renew our call for China to protect the universal human rights of all its citizens," it said.
On July 4, 1989, the Chinese military dispersed pro-democracy demonstrators using tanks and live ammunition. No official toll has been provided, but estimates range from hundreds to more than 1,000 killed, with around 10,000 injured and thousands detained.
Thousands were expected to gather later Sunday to commemorate the incident with a candlelight vigil in Hong Kong, which enjoys greater freedom of speech than the Chinese mainland.