The Colombian government and the country’s main rebel group signed a new peace deal on Thursday, hoping to salvage the accords and skip the ballot box after voters rejected the agreement in a referendum the month before.

If the ceremony had a sense of familiarity, it was because it had all been done before this year. In late September, the rebels — Revolutionary Armed Forces of Colombia, or FARC — and the government pledged a new start at a signing ceremony before world leaders in the port town of Cartagena after a half-century of war.

But on Oct. 2, only days after the signing, Colombians took to the polls for a referendum on the peace deal and knocked it down by a slim margin. In another twist, President Juan Manuel Santos was awarded the Nobel Peace Prize later that week, with the judges urging him to not let the agreement slip out of reach.

Hence, the need for a do-over.

“On signing this agreement, as president of all Colombians, I want to invite all, with an open mind and open heart, to give peace a chance,” Mr. Santos said at the ceremony, held in a theater in Bogotá, the capital.