Colombian President Juan Manuel Santos opened a new national dialogue Monday to seek peace with FARC rebels as both sides scrambled to revive a peace deal to end the half-century conflict.

In a televised address a day after voters rejected the agreement in a referendum, Santos said he had asked the government's chief negotiator Humberto de la Calle to "begin discussions as soon as possible addressing all the necessary issues to have an agreement and realize the dream of every Colombian to end the war with the FARC."

Monday's announcement came after Santos, who has staked his legacy on ending the 52-year-old conflict, called an emergency meeting with leaders of the country's political parties to try to chart a way forward after Sunday's shock referendum defeat.

The leader of the Revolutionary Armed Forces of Colombia (FARC), Rodrigo Londono, meanwhile said in a video from Havana where the peace talks were held that the Marxist guerrillas, like the government, remained committed to an ongoing ceasefire.

Londono, better known by the nom de guerre Timoleon "Timochenko" Jimenez, said the rebels were prepared to "fix" the rejected deal. The result "does not mean the battle for peace is lost," he said.

U.N. Secretary General Ban Ki-moon, who had offered a UN team to oversee the disarmament process, said he had "urgently" sent his Colombia envoy to Havana, where the four-year talks have been held, for new consultations. But the outcome left no clear path to end a conflict that has claimed more than 260,000 lives and left 45,000 missing.

Opinion polls had showed the "Yes" camp well ahead, and negotiators had said there was no Plan B in the event of a "No" vote.

The peace deal had been hailed as historic from the time it was concluded on Aug. 24 to the moment it was signed last week in the presence of Ban and U.S. Secretary of State John Kerry. But many Colombians resented the blood shed by the Marxist guerrillas and the lenient punishment the deal meted out for their crimes. Voters rejected the agreement by a razor-thin margin: 50.21 percent for the "No" camp to 49.78 percent for "Yes." Voter turnout was low, at just over 37 percent. Although a referendum was not required to adopt the deal, Santos insisted on holding one to ensure its legitimacy.

Forecasts apparently miscalculated Colombians' desire to punish the FARC. The accord called for the FARC's 5,765 rebels to disarm and the group to become a political party with guaranteed seats in Congress. That did not sit well with some Colombians who remember the FARC for massacring civilians, seizing hostages and sowing terror in a multi-sided conflict that has seen atrocities committed all around.