On the campaign trail, Mr. Duque has said Mr. Uribe, who cannot run for president again because of term limits, is the country’s “eternal president.”

“Álvaro Uribe transformed Colombian politics. His legacy is everywhere, and he remains an important political player,” said Michael L. Evans, a senior analyst at the National Security Archive, an investigatory nonprofit that provided The New York Times with the cables after petitioning that they be declassified.

He added: “In these cables we learn more about the allegations that most worried the Embassy: the aviation licenses for cartel figures; his financial ties to the Ochoa clan; and above all the possibility that he might be indebted to them.”

Mr. Uribe served as president from 2002 to 2010 and was considered America’s closest ally in the region in the war against drug traffickers. He negotiated a deal to demobilize paramilitary groups in 2004 and delivered the blows to leftist rebels that led to a peace deal under his successor in 2016. Both were financed by the cocaine trade.

But questions persist about possible connections between Mr. Uribe and illegal activity.

Colombia’s Supreme Court has ordered an investigation into a witness-tampering case against Mr. Uribe involving the Bloque Metro, a paramilitary and drug trafficking group based in Medellín. Mr. Uribe’s brother, Santiago, is awaiting trial on charges that he ran a death squad called the Twelve Apostles from his ranch.

The American cables offer a window into the accusations Mr. Uribe faced during his political rise.

In the 1990s, a time marked by escalating drug violence and corruption in Colombia, Mr. Uribe emerged as a “young leader with a rosy future” and a “bright star on the Colombian political scene,” the diplomatic cables say.

However, diplomats also came across accusations that tarnished that reputation.

Mr. Vélez, the senator who said Mr. Uribe’s campaign was financed by the Ochoa drug family, told diplomats about a meeting that was arranged in the 1990s between Mr. Uribe, two other politicians and the wife of Mr. Escobar. The meeting had been secret until Mr. Escobar published a letter about it, and the diplomats wanted to know how it had come about.