Horacio Serpa: Polls say he is one of Colombia's most disliked politicians

Mr Uribe is still well clear of his nearest rival, Liberal party candidate Horacio Serpa according to the poll by Invamer Gallup and Centro Nacional de Consultoria.

But should the elections go to a second round, Mr Uribe might find his lead narrowed, as the votes for the other moderate runners up might well go against the bespectacled 49-year-old lawyer.

Mr Uribe has climbed to the top of the polls with his talk of getting tough with the country's Marxist rebels.

He has been a fierce critic of outgoing President Andres Pastrana's failed attempts to negotiate peace with the Revolutionary Armed Forces of Colombia, (FARC).

Bomb attack

Mr Pastrana, who broke off talks with FARC in February, is constitutionally barred from re-election. He would have no chance of winning anyway, polls show.

If Mr Uribe wins in the first round that will be unprecedented.

He will also break the monopoly the traditional Liberal and Conservative parties have held on power since Colombia's independence from Spain in 1819.

Campaigning under the slogan "Firm Hand, Big Heart", Mr Uribe, whose landowner father was killed by FARC during a botched kidnapping attempt, has promised to create a network of a million civilian informers, armed with radios, to help the security forces.

'Warmonger'

On Saturday, Mr Uribe, who has cancelled all public appearances since escaping a FARC bomb attack in April, urged Colombians not to let up in their determination to vote for a government "committed to defeating violence".

Mr Serpa, a 59-year-old former interior minister who says he favours dialogue with rebels, has strived to chip away at Mr Uribe's rock-solid lead by portraying his rival as a "warmonger".

But Mr Serpa's past association with disgraced former President Ernest Samper, who ruled from 1994-98 and was accused of having received $6 million in campaign contributions from the Cali drug cartel, has also made him one of Colombia's most disliked politicians, according to many polls.

"The real poll that counts is voting day. I'm going to be elected Colombia's next president in the run-off," Mr Serpa said on Saturday.