Colombian Defense Minister Juan-Manuel Santos, who oversaw operations to rescue Colombian-French hostage Ingrid Betancourt from FARC rebels, resigned on Monday, eyeing a possible run at the presidency.
"I believe it is necessary to hand over the baton and to continue my public life on another stage," he told a press conference.
Santos, 57, said he would run in the country's presidential elections in 2010 but only if the current head of state, Alvaro Uribe, is not a candidate.
"If he does not stand for re-election, then I will be a candidate," said Santos, a conservative who has been the country's defense minister since 2006.
Under the Colombian constitution all ministers eyeing a run at the presidency have to quit their posts at least a year before the elections.
Uribe has not said if he will stand, although under the current constitution he is barred from seeking a third consecutive mandate. If he does decide to run, his supporters have proposed organizing a constitutional referendum to allow him to stand for a third term.
Opinion polls have put Santos ahead in the vote if Uribe is not a candidate.
He orchestrated the successful rescue in July 2008 of Betancourt and 14 other hostages, most of whom had been held for years in the jungles by Marxist FARC rebels.
He also authorized the bombing of a FARC camp in Ecuador in March 2008, in which 25 rebels were killed, including their number two Raul Reyes.
Quito broke off ties with Bogota over the raid, which have still not been reestablished.
Santos, who has also held portfolios in trade and in the treasury, has a degree from Harvard University as well as the London School of Economics. A journalist by training, he comes from a family of press barons.