More than three years into marathon peace talks to end Latin America's last civil war, Colombia and Marxist FARC rebels missed their self-imposed deadline, but pledged to keep trying.
"To be perfectly frank, we do have to tell the public that at this time, there are still some differences with the FARC on significant issues," said the government's lead negotiator, Humberto de la Calle.
The lead negotiator for the FARC, Ivan Marquez, said "it was not possible. Because the logical demands of a long and complicated war like that which Colombia has endured made it that way."
The government and the Revolutionary Armed Forces of Colombia (FARC) had shown signs earlier in the week that they were not closing in on a done deal. They have reached agreement on most of the points on their agenda.
But they still have to iron out agreement on a bilateral, final ceasefire that includes the rebels laying down their arms and a deal on how to ratify any accord they reach.
De la Calle said the two sides would keep pushing forward, this year, and not necessarily in Havana indefinitely.
"We are going to give it our utmost to get a final deal struck. But that takes timely decision-making. It's what Colombians want. Excuse me, it is what they are demanding," he added.
Negotiators at the talks -- held in the Cuban capital since November 2012 -- had announced several key advances in recent months.
The goal is to turn the FARC from a rebel group into a political party, ending a grinding, complex conflict that has killed more than 260,000 people and uprooted 6.6 million.
Hostilities have almost entirely halted under the FARC's unilateral ceasefire, although a smaller rebel group, the National Liberation Army (ELN), has not joined the peace process and continues periodic attacks. It has however begun preliminary talks with the government on entering into formal peace negotiations.
The ELN freed early Thursday a 40-year-old civil servant it had taken hostage in September of last year, Santos said on Twitter.
Santos has said the ELN has to free all captives as a condition for starting peace talks.