Bogota: The race for Colombia's presidency began yesterday, with former defence minister Juan Manuel Santos the favourite after the South American nation's popular incumbent was blocked from running for a third term.

The Constitutional Court's decision to bar a referendum on re-election heralds an end to President Alvaro Uribe's eight-year rule, during which the US ally beat back left-wing guerrillas, stabilised its economy and drew investors.

With Colombian politics fixated for more than a year on the re-election issue, and polls showing Uribe would have won easily if allowed to run, Friday's ruling represented a starting gun for other presidential aspirants.

"The happiest man in Colombia today is Juan Manuel Santos," said one of his rivals in the May 30 presidential election, Gustavo Petro, of the leftist Democratic Pole party.

Uribe's former defence minister — who also held the finance portfolio in a previous government — is closely associated with the US-backed security policies that have made Uribe the nation's most popular president, and helped Colombia escape its past image for violence and chaos.

"The continuity of President Uribe's policies are at stake," said Santos, confirming his candidacy and rallying supporters. "We can't re-elect him, but let's re-elect democratic security, social cohesion and investor confidence."

Before the presidential vote, a March 14 parliamentary election will test the political waters, and a certain amount of realigning among Uribe's ruling coalition is expected.