United Nations Secretary-General Kofi Annan has said he hopes Kenya will have a new constitution very soon.
Police are launching a "high-powered" investigation into the Kisumu riots
He met Kenyan President Mwai Kibaki on Thursday, a day after police in the western town of Kisumu fired on demonstrators demanding swifter change.
Police have launched an inquiry into the riots in which one person died.
Opposition parties accuse President Kibaki of delaying the introduction of a constitution that would reduce his powers, a charge he denies.
The issue has also split the ruling Narc coalition.
"We had discussions on the constitution review process and I hope all these will go on smoothly in a satisfactory and peaceful manner," Mr Annan said at a press conference in the Kenyan capital, Nairobi.
Meanwhile, an investigation into why police fired live bullets at rioters in Kisumu instead of rubber bullets or teargas is underway, reports Kenya's Daily Nation newspaper.
Commissioner Hussein Ali said the police will investigate the conduct of police officers and "the circumstances under which this unfortunate incident occurred", the paper reports.
The Kisumu demonstrators were angered by the slipping timetable for the introduction of the new constitution which on the recommendation of the constitution review body would include the new powerful post of prime minister reducing the president's powers.
The BBC's Caroline Karobia in Nairobi says a rally planned for Friday, organised by a lobby group pressing for the new constitution, has been cancelled, but from next week a series of rallies will be held across the country culminating with a major one in Nairobi in early August.
After coming to power in December 2002, President Kibaki's ruling Narc coalition promised to introduce a new constitution within 100 days, but the deadline was put back to 30 June this year, before being again postponed.
Mr Kibaki said political divisions along ethnic lines had hampered progress with the constitutional review, but that he remained committed to having a new constitution.
To shore up his authority, Mr Kibaki last week brought members of the former ruling Kanu party into government.