Meet Gustavo Petro, Colombia's first leftist president 3:41
(CNN) --
Gustavo Petro's victory in Colombia's presidential election this Sunday opens a new page in the history of the country's relations with the United States.
Colombia, which has never had a leftist president, has been Washington's closest ally in the region for decades.
But the election of Petro, a former leftist guerrilla, to the country's highest and most important post could radically change that relationship.
In an interview with CNN last week, Petro said he intends to renegotiate Colombia's trade deals with the US.
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He also plans to open a dialogue around three main issues: protecting the Amazon rainforest, ending the war on drugs, and moving the Colombian economy away from extractive projects like fossil fuels.
His future talks with US President Joe Biden are likely to be difficult, with the two leaders diametrically opposed on issues such as relations with Venezuela.
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Although he tried to distance himself from the regime of Venezuelan dictator Nicolás Maduro on the campaign trail, Petro supports recognizing the authoritarian leader as the country's president, something the White House is firmly against.
But the two presidents could still find common ground in areas such as environmental protection and the energy transition.
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And Petro has his own allies in Washington.
The president-elect told CNN that he speaks "often" with US Senator Bernie Sanders and met in person earlier this year with the Progressive Caucus, a group of left-leaning US representatives.
Colombia's president-elect has also spoken of a desire to create a new progressive alliance in South America.
This would probably involve the president of Chile, Gabriel Boric, and that of Argentina, Alberto Fernández, instead of the three countries considered authoritarian by the US: Cuba, Nicaragua and Venezuela.
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Biden recently fueled opposition among some Latin American leaders by excluding those three nations from the Summit of the Americas, a regional forum held in Los Angeles in early June.
In solidarity, the president of Mexico, Andrés Manuel López Obrador, decided to skip the event altogether.
But Petro told CNN that he would have attended anyway.
"Of course," he said.
“He would have gone and (would have) told Biden that it was wrong not to invite some countries, but he would never turn down an opportunity for dialogue.”
Gustavo Petro