Ivan Marquez, a senate candidate and senior member of the political party formed by the former Revolutionary Armed Forces of Colombia rebels, told reporters that party members decided not to field a candidate after Londono underwent open heart surgery on Wednesday.

Since the peace deal struck with the government of outgoing President Juan Manuel Santos in 2016, the FARC gave up its half-century armed struggle and became a political party keeping the same acronym.

Colombia's presidential election is scheduled for May 27, with a possible runoff vote set for mid-June.

Surveys showed that Londono -- candidate for the Common Alternative Revolutionary Force -- had just one percent voter support.

Marquez however said his party is not dropping out of the legislative elections set for Sunday. The peace agreement guarantees at least ten seats for the FARC, but they must campaign for them.

Londono suffered a heart attack last week at the end of his daily exercise routine. He has had serious health scares before: in 2015 he had a heart attack in Cuba while negotiating the peace deal, and in July 2017 he suffered a minor stroke.

The ex-rebel leader is undergoing a "satisfactory" recovery, Marquez said.