Security is tight in the Pacific island state with soldiers from Australia and New Zealand stationed around the capital as politicians, diplomats and dignitaries converged for talks.
"A few metres away, buildings lie burned, bodies have been retrieved from the ashes and our capital is silent as it has never (been) before," said the king.
He said plans under discussion would see elections for 21 of the 30-member legislature starting in 2008. Currently the majority of members are appointed.
He attributed the delay in implementing reforms to differing opinions which were "not irreconcilable and can be resolved through dialogue".
Much of the center of Nuku'alofa lies in ruins after the violence and the king said reconstruction of the area would cost many millions of dollars.
Businesses owned by ethnic Chinese were particularly badly hit.
While pro-democracy politicians and businessmen were accused of orchestrating the riots to unseat their rivals.
Democracy campaigners in turn have blamed the government for allowing public anger over the pace of reform to boil over.