The latest peace deal between the Colombian government and the rebel group known as FARC is one step from approval after the country's senate voted in favor of the agreement on Tuesday.
The lower house of Congress is considering the measure Wednesday.
A previous version of the agreement was struck down in a national referendum, but the revised deal signed last week in Bogota by President Juan Manuel Santos and FARC leader Rodrigo Londono needs only to be approved by lawmakers and not the public.
The 75-0 vote in the senate came after more than 12 hours of debate among lawmakers, government officials and victims of rebel violence.
Humberto de la Calle, the lead government negotiator, said the current peace is fragile and urged lawmakers to back the deal, saying this is a "crucial moment for Colombia."
President Santos, who was awarded the Nobel Peace Prize for his efforts to end the 52-year war, expressed his gratitude after the vote, saying the senate is "committed to the peace we long for."
Colombia's former leader, Alvaro Uribe, said there were some improvements among the more than 50 changes made to the deal since last month's referendum. But he said his party could not vote for the new deal and has always endorsed direct democracy.
Senator Nohora Tovar Rey, another member of Uribe's party, also criticized letting lawmakers decide instead of citizens.
"Congress approved the agreement that the Colombian people rejected. It is ignoring the will of the majority," she said.
Peace negotiations have stretched on for four years in the effort to end the conflict that has killed more than 220,000 people and displaced millions. Santos has said there is no more room for negotiation.