The Ugandan Lord's Resistance Army (LRA) has announced a unilateral ceasefire, with immediate effect.
Otti said he spoke on behalf of the LRA leader
The rebel movement's deputy leader Vincent Otti told the BBC he had ordered all field commanders to cease all hostilities against Uganda's army.
Ugandan Interior Minister Ruhakana Rugunda said his government would wait to see what happened on the ground, in response to the announcement.
The peace talks are due to resume in the Sudanese town of Juba next week.
In a phone call to the BBC's Focus on Africa programme, Mr Otti announced: "I, Lt Gen Vincent Otti, second in command of the LRA, by the order of Gen Joseph Kony, chairman of the LRA High Command, do hereby declare a unilateral cessation of hostilities.
"I order all our field commanders to, with immediate effect, cease all form of hostilities against the Ugandan People's Defence Forces (UDPF) positions and others.
"I do hope that the government of Uganda shall reciprocate this gesture of goodwill so that the warring parties may finally find a bilateral agreement to provide a peaceful atmosphere for our people," Mr Otti said.
The LRA rebel movement has refused to send its most senior leaders to peace talks with the government.
Southern Sudanese vice-president and head mediator, Riek Machar had asked for the group's top leaders to take part after earlier peace talks failed.
On Thursday Mr Otti told the BBC that Juba was not safe because an International Criminal Court (ICC) warrant for the LRA leaders' arrest was still in force and Ugandan government forces were present in the town.
On Tuesday, Mr Kony held his first formal meeting with Mr Machar and a Ugandan official in a forest clearing on the border between Sudan and the Democratic Republic of Congo.
This was hailed as a significant move, since the failure of earlier talks had been attributed in part to the negotiators not being sufficiently high-ranking to strike a deal.
Ugandan President Yoweri Museveni has offered the rebels a full and guaranteed amnesty and protection as long as they renounce violence.
Thousands of civilians have died in the 20-year conflict and more than one million have been forced to flee their homes.