Colombian voters will back a peace deal with Marxist FARC rebels in a plebiscite, according to an opinion poll released on Wednesday, in encouraging news for President Juan Manuel Santos, who wants voters to ratify an end to more than 50 years of war. Negotiators are hammering out final details of the deal at talks in Havana. The constitutional court recently ruled that a vote can take place following the publication of the full accord and six weeks of campaigning. The survey, conducted by polling firm Invamer on behalf of local media Caracol Television, Blu Radio and El Espectador newspaper, showed 67.5 per cent of those voting would approve the deal, while 32.5 per cent would vote against it. To make the vote's result binding, the winning side would need a majority of votes cast and support totaling at least 13 per cent of the country's 33 million eligible voters. Colombia's principal opposition party, headed by hardline former President Alvaro Uribe, has said it will campaign for a 'no' vote.