Officials from the two rebel groups made the announcement after talks with Libyan officials trying to mediate in the conflict.
"We announce in front of Colonel al-Qadhafi that we are completely committed to a ceasefire," Khalil Ibrahim, senior official of the Justice and Equality Movement, said to a round of applause from a gathering of about 200 political, tribal and military personalities attended by the Libyan leader Muammar al-Qadhafi.
"And we declare that we agree to resume negotiations ... without any preconditions," he added.
"And we declare that we agree to resume negotiations ... without any preconditions"
Justice and Equality Movement
Representatives from the two groups, the Sudan Liberation Movement and Justice and Equality Movement, said they would discuss any demands they had during the talks and not have them as conditions for the talks.
There was no immediate comment from the Sudanese government, but the rebels' statement could boost efforts to resume peace talks.
A ceasefire between the rebels and the government, and militias allied to it, has been largely ignored in past months, with violence continuing in the large area of western Sudan where the UN estimates that 180,000 people have died since February 2003, mainly from war-induced hunger and disease.
Hilal's tour of Darfur is being
viewed with suspicion by some
The Sudan Liberation Movement meanwhile slammed the Sudanese government for what it called was "attempts to portray the crisis in Darfur as just a tribal conflict".
The group also decried the tour being undertaken by tribal leader Musa Hilal in the region as a "government plot to escalate tensions".
Hilal, an Arab tribal chief accused by the United States of being a leader of "Janjawid" militia is now touring Darfur with a message of peace and reconciliation.
He and other tribal leaders in the western Sudanese region, including some from non-Arab groups, are taking part in a government-sponsored initiative to persuade villagers displaced by two years of fighting to return home.