Colombia's government and leftist rebels have missed the target for reaching a deal to end the country's half-century conflict.

After a breakthrough in long-running talks six months ago President Juan Manuel Santos set Wednesday as a deadline to wrap up negotiations. But negotiators for the government and Revolutionary Armed Forces of Colombia say substantial differences still exist and more time is needed to conclude the talks.

The FARC had cautioned that expectations for reaching a final deal by Wednesday were overly optimistic, but momentum had been building in recent weeks toward a bilateral ceasefire.

This week U.S. Secretary of State John Kerry paid a visit to the negotiating teams while in Cuba, telling both sides they can't afford to fail in bringing peace to the South American nation.