"We have decided to re-establish diplomatic relations," Santos said before turning to embrace Ecuador's President Rafael Correa at a summit of South American presidents in Guyana. "We are going to name ambassadors before Christmas."

In March 2008, Colombia bombed a guerrilla camp across the border with Ecuador, killing guerrilla leader Raul Reyes and triggering a regional crisis in an attack coordinated by Santos, who was defense minister at the time.

Ecuador withdrew its ambassador and broke off relations in protest. Relations have warmed considerably in recent months.

Since taking office in August, Santos has moved quickly to repair ties with Ecuador and fellow neighbor Venezuela.

Former Brazilian President Luiz Inacio Lula da Silva described a budding friendship between former ideological foes Santos and Venezuelan President Hugo Chavez as a "political miracle."

Chavez and Santos, bitter ideological rivals before the Colombian took office, smiled and laughed at the meeting, their third encounter in three months.

Venezuela on November 26 said it will restart crude shipments to Colombia in a further sign of warming ties between the countries, which are also moving to restore billions of dollars of annual trade lost in recent years.