Colombia's President Juan Manuel Santos says peace with the Farc rebel group will boost economic growth and enable the country to rebuild its social fabric.
"War is always more costly than peace," he said in an interview with the BBC.
Mr Santos and Farc leader Timoleon Jimenez, known as Timochenko, will sign a historic peace deal later on Monday.
But it will take a long time for Colombian society to recover from more than five decades of conflict, he said.
The Farc will be relaunched as a political party as part of the deal, which is due to be put to Colombian voters in a popular vote on 2 October.
"We could have grown between 2% and 3% more per year for the past 23 years," Mr Santos told the BBC's Lyse Doucet, adding that the conflict had also had a profound impact on Colombian society.
"We have even lost our compassion, which is the ability to feel some kind of pain for others.
"A country at war for 50 years is a country that has destroyed many of its values," said President Santos.