Exiled democracy activist Wei Jingsheng called at the weekend for greater unity among dissident groups.
He told 100 other exiled dissidents they had to remember their responsibility to people on the mainland.
'We should put our minor arguments aside and be more unified. Our forces have to be strengthened,' said Mr Wei, who was addressing a candlelit vigil at the University of Toronto to commemorate victims of the June 4 crackdown nine years ago.
Mr Wei said: 'Maybe one day we can go back to the mainland. Then, we have to tell our people we have done well overseas.' His comments came as two pro-democracy groups, the Chinese Alliance of Democracy and the Federation for a Democratic China, called for a world conference in New York in July, to try to form a coalition among exiles.
Alliance chairman Frank Woo Fangcheng said he hoped all dissidents overseas would attend the meeting.
'We need such a coalition to push our work ahead,' he said.