Andres Pastrana, the main defender in Washington of Colombia's cooperation in the war on drugs, said Uribe's support for Ernesto Samper, whose U.S. visa was revoked because of alleged ties to drug traffickers, "left him without a choice but to resign."
"This changes Colombia's policy and it changes it radically," said Pastrana, after more than six hours of closed-door meetings with officials in Bogota.
Pastrana's resignation, which caught Uribe and most Colombians by surprise, was deplored by the president in a written statement. In a swift, impromptu shuffling of the nation's top diplomats, Uribe named foreign minister Carolina Barco as the new ambassador in Washington.
The government's announcement Monday that it was nominating Samper for the Paris post sparked outrage among many Colombians and allies in Washington in the war on drugs. In his statement, Uribe said Samper had declined the France ambassadorship so as not to harm Colombia's national interests.
Uribe former culture minister Maria Consuelo Araujo, a key aide in Uribe's recent re-election campaign, would be the new foreign minister and the current ambassador to the United Nations, Maria Angela Holguin, would take over diplomatic duties in Paris.
Pastrana, who was president himself of Colombia between 1998-2002, had flown back to Colombia on Monday after the foreign minister announced Samper's selection.
The two statesmen are longtime political rivals, with Samper narrowly defeating Pastrana for the presidency in 1994. Samper served as president until 1998.
Samper was nearly impeached over allegations his campaign accepted $5 million in contributions from the Cali cocaine cartel. He was cleared by Colombia's legislature of wrongdoing, but saw his visa to the U.S. stripped and top aides sent to jail.
On Tuesday, Myles Frechette, a former U.S. ambassador to Colombia, called Uribe's appointment of Samper an "incredibly maladroit" move that could stir the U.S. Congress to curtail its support for the country's counter-narcotics efforts.
Colombia is one of the largest recipients of U.S. aid, having received more than $4 billion since 2000.