Tanzania has been celebrating the 40th anniversary of the union between the island archipelago, Zanzibar and the mainland Tanganyika.
Speaking at the Amani National Stadium in Zanzibar, President Benjamin Mkapa called for the union to be maintained at all costs.
Some Zanzibaris feel they are getting a bad deal
He said that, as in any marriage or community, problems were inevitable, but solutions must be found that consolidated Tanzania's unity.
"Our union is a demonstration that where there is political will, Africans can unite," he said.
The two former sovereign states sealed their union following the departure of the British colonial authorities at the beginning of the 1960s.
The union has allowed Zanzibar to remain semi-autonomous with its own president while benefiting from the economic and political clout of the mainland.
It has outlasted huge political change not least the move away from a socialist to a capitalist system.
The BBC's Daniel Dickinson says the durability of the union suggests it is working and he says there are no realistic moves towards Zanzibar becoming independent.
The main opposition party in Tanzania, the Civic United Front, which has its stronghold on the islands believes that Zanzibaris are getting a bad deal.
It points to falling living standards and the deterioration of roads, schools and health services.
It also says islanders have no real political voice and are, as a result treated as second-class citizens.
But these problems are not unique to the islands, our reporter says.
Tanzania has been suffering from an economic downturn and is only now beginning to recover.
How this growing wealth is used on the mainland and the island archipelago will reflect whether or not fears of second-class citizenship have a basis in fact.