During the conference a letter from Peter Liang's mother was read, which revealed that Liang quit a federal government job to enter police training school for public service.

"The accident happened last year led us to the lowest point in life. I feel sorry for the victim and Peter. I wish society would give us a fair outcome," the mother said.

The father of Jianwen Liu, the Chinese-American New York police shot dead by a black man while working last December, also attended the conference to express his concern for Peter.

Liang's case has caused national wide attention in the United States, as more than 130,000 people have signed their name on the letter to the White House, Chen said.

He urged the Chinese to play a more active role in American politics.

"It is necessary to draw attention from society, however as the judicial system is independent in the United States, we still need justice to deal with this case."

In December 2014, Liang, an NYPD officer placed an unarmed black man in a chokehold during a confrontation. Grand Jury's decision not to charge him led to a nationwide protest.

Ten days later, two policemen, including Wenjian Liu, were killed by a black man, which has intensified tensions between the police and the black in the United States.