The decision was taken after top rebel and army officials met for a crucial round of talks in the capital.
Alain Richard Donwahi, head of the national disarmament commission, said on Saturday that the process would last until 10 August.
He spoke in Yamoussoukro, where delegations led by rebel forces chief of staff Colonel Soumaila Bakayoko and army chief Colonel Philippe Mangou met with other top officials.
"The work was difficult, and it took place sometimes under pressure," Donwahi said. "But the results were convincing."
Earlier, a rebel official said no start date would be announced until enough money was available to underwrite the campaign, which is expected to cost $150 million.
But Donwahi said most of the money already had been pledged.
"The work was difficult, and it took place sometimes under pressure. But the results were convincing"
Alain Richard Donwahi,
National disarmament commission chief
The World Bank has agreed to pay 47%, while the government will pay 29%, and 13% more will be paid by the UN Development Programme, the European Union and other donors.
The government still needs donors to come up with the remaining 11%, Donwahi said.
Prime Minister Seydou Diarra said the agreement was proof that "peace is irreversible".
South African President Thabo Mbeki brokered a peace deal last month to end the country's civil war, sparked by a failed coup in September 2002 that left the northern half of the world's largest cocoa grower in rebel hands.
Mbeki, as the African Union mediator in the conflict, had called for a nationwide disarmament campaign to begin mid-May.
Laurent Gbagbo says elections
will take place on 30 October
Earlier attempts to begin disarmament also met with repeated failure.
In late April, both sides pulled back heavy weapons from front-lines that divide the nation, where about 10,000 UN and French troops have been deployed to bolster security and help prevent all-out war.
President Laurent Gbagbo's government said long-awaited presidential elections will be on 30 October.