In a joint statement, the Revolutionary Armed Forces of Colombia, or FARC, and representatives of Colombian President Juan Manuel Santos, called the new accord on point No. 2 of their six-item agenda an important achievement.
"We have arrived at a fundamental accord ... for the end of the conflict and the building of a stable, lasting peace," it said.
The two sides said the deal calls for the rebels to disarm and form a political movement.
"The signing and implementation of a final agreement will contribute to the expansion and deepening of democracy, in that it will imply the laying down of arms and the prohibition of political violence for all Colombians," said the statement read to journalists by Rodolfo Benitez, a Cuban official helping facilitate the discussions.
Talks have been held in the Cuban capital over the last year.
They are set to pause before resuming Nov. 18 and focusing on a new point, drug trafficking. Earlier this year negotiators announced a partial agreement on the first agenda item, agrarian issues.
The deals on land and political participation represent the greatest advance toward peace since the 1980s, said Hector Riveros, who was point person for peace under former Colombian President Cesar Gaviria, who served from 1990 to 1994.
"Also, they have moved past two of the most complicated elements in the process," Rivero said by phone from the Colombian capital, Bogota. "The process has six points. The last one is implementation. ... We've already done two, which means we're 40 percent of the way there, so I believe there is a degree of significant movement."
The talks in Havana are the fourth attempt since the 1980s to reach peace.
The other three fell apart amid disagreements, mutual recriminations and flare-ups of violence.
Although the statement emphasized that much work remains, lawmaker Ivan Cepeda of the leftist Alternative Democratic Pole party called Wednesday's agreement "a great victory for peace."
"This situation that presents itself today in Havana truly is cause for optimism and the conviction that it is possible to end this story of political violence," Cepeda said.
Although months frequently pass and talks recess without major announcements, the deal on point No. 2 shows that "the negotiators of the government and the FARC are not drinking daiquiris on the beach," he added.
A key element of the deal is the creation of "special constituencies" in regions hit hardest by the conflict.
That means essentially that representatives of political, popular and social movements arising from a final peace accord would have a transitional representation in Congress.
The statement did not give details, such as how many seats could be involved.
After the statement was read, the two sides gave separate and optimistic assessments of the deal.
"We are seeking reconciliation. May politics be free of intimidation and violence," said Humberto de la Calle, Santos' lead negotiator.
"Colombia is living a springtime of dreams for justice," said Ivan Marquez, a top FARC commander whose birth name is Luciano Marin Arango.
Associated Press writers Vivian Sequera, Cesar Garcia and Libardo Cardona in Bogota contributed to this report.
Andrea Rodriguez on Twitter: www.twitter.com/ARodriguezAP