BOGOTA, Colombia (AP) — President Juan Manuel Santos said Friday he will have Colombia's congress ratify a modified peace deal with the nation's largest rebel group after voters rejected the first pact last month in a referendum.

Speaking in Washington, Santos said implementing the accord in the shortest time possible would prevent a fragile cease-fire from falling apart. His comments came after two rebels of the Revolutionary Armed Forces of Colombia were killed in combat with security forces during a confusing incident now being investigated by United Nations-sponsored monitors.

Santos announced a week ago that FARC agreed to modify the peace accord defeated in a referendum, but he had been cagey about how he intended to implement the deal. Officials said no decision had been made on whether the modified deal might be presented to voters in another referendum.

Santos was addressing the Organization of American States after the hemispheric group endorsed the deal.

The accord is intended to end a half-century-long conflict that has claimed more than 220,000 lives and driven almost 8 million people from their homes.