In a video address shared on social media on Tuesday, De la Espriella alleged that Petro and Historic Pact candidate Ivan Cepeda were trying to overturn the election result.

"Petro and Cepeda launched their plan B to remain in power no matter what. And they want to do it through a coup d'etat," he warned.

De la Espriella claimed the situation had worsened in recent hours, accusing Petro of exceeding his authority by rejecting the election outcome and declaring Cepeda the winner.

"Cepeda, playing the good cop, is calling for civil disobedience so as not to recognise the votes that, in democracy, in freedom, the Colombian people cast at the ballot box to make me president of all," he added.

The president-elect appealed to Colombia's armed forces to uphold the Constitution and defend the country's democratic institutions. He also urged the international community to remain "watchful, attentive, and supportive of us."

De la Espriella further alleged that Petro and Cepeda were seeking to avoid future investigations.

"Added to this is the fear that both Petro and Cepeda have of the revelations to come, not only regarding all the corruption that ran rampant during these four dark years of government , but also the legal consequences their ties to narcoterrorism will bring, both with criminal groups inside Colombia and with the cartel led by the narco-dictator Nicolas Maduro," he said.

Political tensions increased after Carlos Alonso Lucio, a member of De la Espriella's transition team, said Petro should "be tried" and could face extradition to the United States if requested by US authorities.

De la Espriella later announced the suspension of the presidential transition process with the outgoing administration.

Finance Minister and transition coordinator German Avila subsequently halted transition meetings, saying remarks made by members of the incoming administration had jeopardised the process.

Speaking behind bulletproof glass, de la Espriella told supporters that voters had rejected corruption, armed groups and the political establishment.

“We have defeated the rifles that threatened hundreds of thousands of our compatriots in the territories that the government handed over to narco-terrorist groups. We have defeated at the ballot box the corruption that tried to buy votes and failed. Therefore, my fellow citizens, let us recognise a victory for the people , a people who have spoken. And the people must celebrate this triumph,” he said.

While celebrating the outcome, de la Espriella also called on supporters to closely monitor the vote-counting process as authorities move toward the official certification of results.

“Take care of the votes. Let the lawyers be vigilant, ready to protect what the people have decided. To all Colombians, activists, defenders of the homeland, influencers, friends, and members of the Tiger pack: social media will continue to be our bastion of democratic struggle,” he went on to say.

The candidate said a future administration under his leadership would focus on restoring state authority, tackling organised crime and strengthening ties with countries that respect democratic institutions and the rule of law.

Supporters at the event welcomed the result and expressed hope that a new government could create better opportunities for younger Colombians.

With nearly all polling stations reporting, preliminary election figures place de la Espriella in first place with 12,959,542 votes, representing 49.66 percent of ballots cast. Ivan Cepeda follows with 12,708,712 votes, or 48.70 percent.

Under Colombia's electoral system, the preliminary count is followed by a scrutiny process in which vote tallies are officially reviewed and certified before final results are confirmed.

The outcome highlights a deeply polarised political landscape, with voters largely backing candidates from either the political right or left, while centrist contenders failed to gain significant support.

The runoff campaign is expected to focus on issues including security, drug trafficking, economic management, democratic institutions and the legacy of President Gustavo Petro’s government.

Speaking to supporters after advancing to the second round, de la Espriella presented the election as a defining moment for the country.

“This is tyranny or institutionality. The past or the future, complicity or independence and patriotism,” he said. “There is no more room for indifference.”

He also accused his rival of links to criminal groups, describing Cepeda as “a bandit allied with narco-terrorists.”

De la Espriella said that if elected, he would uphold judicial independence, work with local governments regardless of political affiliation, reduce poverty, strengthen security, combat drug trafficking and restore state authority across Colombia.

Cepeda, meanwhile, criticised what he described as foreign involvement in the election after Ecuadorian President Daniel Noboa publicly congratulated de la Espriella and criticised the left-wing candidate on social media .

“Foreign governments are meddling in our elections,” Cepeda said.

He also called for greater scrutiny of his opponent’s campaign finances and questioned the scale of spending behind the campaign.

Cepeda argued that the runoff represents a choice between preserving social policies advanced under the current administration and a shift toward a conservative government.

“Mr de la Espriella represents fascism, mafia fascism,” he said, warning that social gains achieved during the current government could be reversed if his opponent wins.

The June 21 runoff will determine whether Colombia continues with the left-leaning political agenda associated with the Historical Pact or moves toward a more conservative, security-focused approach under de la Espriella. With the first-round margin relatively narrow, both candidates are expected to intensify efforts to attract voters whose preferred candidates were eliminated, making coalition-building and voter outreach central to the final stage of the campaign.