The mediators presented the offer to the opposition just after armed rebels captured Haiti's second-largest city of Cap-Haitien, diplomatic sources said on Monday.
The opposition was told the international community could call for Aristide's departure before the end of his current term if he failed to adhere to a power-sharing deal.
The opposition has thus far rejected the plan. The rebels have threatened to move on the capital unless Aristide steps down.
The deadline for acceptance of the plan by the warring sides is 5:00 pm (2200 GMT) on Monday, the sources said.
The takeover of Cap-Haitien by the rebels meanwhile has intensified already frantic diplomatic efforts to bring the political opposition on board with the peace plan, the sources said on condition of anonymity.
Armed rebels have threatened
to move into the capital
That plan, which Aristide accepted in full on Saturday, calls for the appointment of a new, independent prime minister and government that will assume substantial powers now held by the president, but allows him to serve out his term which expires in February 2006.
The plan's backers - the United States, Canada, France, the European Union, the Organisation of American States and the Caribbean Community - have to date insisted the elected Aristide could not be removed from office undemocratically.
But if the opposition reverses course and agrees to the deal, the guarantors will vow to put "further political changes" on the table should Aristide violate the agreement, the sources said.
The promise will be made public in a five-point statement to be released in the event the opposition accepts the plan by the deadline, the sources said.