The leaders were also due to discuss regional security
Colombian President Alvaro Uribe has urged the US to give longer prison sentences to drug traffickers extradited from his country.
He said that negotiating short jail terms with traffickers in exchange for information often ended up making a mockery of anti-drug efforts.
Mr Uribe was speaking at an anti-drugs summit of Latin American leaders in the north Colombian city of Cartagena.
Correspondents say it is a rare rebuke from such a strong US ally.
His administration has received billions of dollars in US aid to fight cocaine-traffickers and leftist rebels.
There was no immediate reaction from Washington.
"We are concerned negotiations with drug-traffickers means they are given sentences that are practically indulgent, they become a mockery," Mr Uribe told his fellow leaders.
"The next stage in extradition we want to examine with US officials is that any negotiation with extradited drug-traffickers means they face a minimum severe penalty."
Those attending the summit included Mexico's President Felipe Calderon.
Colombia remains the world's top cocaine producer despite more than $5bn in US aid, Reuters news agency reports.