Commonwealth Secretary-General Kamalesh Sharma has urged Canada to drop its threat to boycott the group's summit in Sri Lanka next year over war crimes allegations.
Canadian Prime Minister Stephen Harper has warned that he may refuse to attend the summit unless Sri Lanka addresses allegations of atrocities during the closing battles of the war against separatist Tamil rebels in 2009.
Sharma, completing a five-day visit to Sri Lanka last week, said the Commonwealth Heads of Government Meeting (CHOGM) in November 2013 should be attended by all nations.
"My message to all leaders is to participate at this (Sri Lanka) CHOGM," he told reporters on after talks in Colombo with President Mahinda Rajapakse.
"I understand a dialogue is going on between the two countries," he said, adding that he hoped the issue would be "resolved" so that Canada could participate in the summit.
The war crimes allegations centre on the Sri Lankan military's final push against the Tamil Tiger rebels before victory for the government ended decades of ethnic bloodshed on the island.
Sri Lanka has denied allegations from international rights groups that government troops killed up to 40,000 civilians while battling Tamil rebels.
Commonwealth countries such as Australia and Canada have been vocal in their calls for Sri Lanka to ensure accountability for rights abuses, placing the issue high on the agenda at the 54-nation bloc's summit last year.
Canada had wanted the Commonwealth to change the venue of the 2013 summit, but other member states turned down the request.