*Updated April 16, 2016 at 4:46 p.m. EST with Pope Francis' comments.

After cancelling his planned visit to a Vatican conference hosting U.S. Sen. Bernie Sanders (D-Vt.) due to schedule complications surrounding his visit to Lesbos, Pope Francis agreed to meet the senator before departing for the small Greek island.

The meeting took place at 6 a.m. at the Vatican’s Saint Martha guesthouse as the Pope was on his way to the airport, Jeffrey Sachs told CNA shortly after the April 16 encounter. Sachs also participated in the meeting along with his wife.

In their discussion, “Senator Sanders thanked Pope Francis for his leadership on the moral economy and his leadership on climate change,” Sachs said.

Additionally, the senator said the Francis’ leadership in the area has led to “a vast difference” in terms of the action taken, and thanked the Pope “for all of his moral leadership and his brave stances.”

Sachs is the director of the Earth Institute at Columbia University and a special adviser to United Nations Secretary-General Ban Ki-Moon on the Sustainable Development Goals. He is also a member of the Pontifical Academy of the Sciences.

The goal of the academy is to foster dialogue between scientists, politicians and various experts, including, at times, those who don’t necessarily share Vatican positions. Sachs, for example, is known to oppose the Holy See’s position on population control.

Sanders and Sachs were present in Rome for an April 15-16 conference on the moral economy which was sponsored by the Academy, headed by Archbishop Sanchez Sorondo.

Pope Francis was initially scheduled to speak to conference participants at 7p.m. April 15, but was “was unfortunately unable to” due to complications in his schedule surrounding his trip to Greece.

The Pope’s presence at the Academy is a common sight, as he frequently pops in for unannounced visits to see what is being discussed.

In their brief meeting with Senator Sanders, Sachs said that Pope Francis apologized for not being able to come to the conference as was previously planned, and thanked the senator for understanding.

Although Pope Francis’ morning meeting with the senator was last minute, it’s nothing out of the ordinary for the Argentine pontiff, who has previously met with other individuals or groups before going on a trip.

One such instance was in 2015 when he was boarding the plane for his 10-day trip to Cuba and the United States. Before getting on bard, the Pope met with a Syrian refugee family that the Vatican is currently housing through one of its parishes.

Pope Francis commented on the brief meeting with Sen. Sanders during a press conference on his return flight to Rome from Lesbos April 16.

“He knew that I was leaving at that time and he had the courteousness to greet me. I greeted him and his wife, and another couple with him that was staying in Santa Marta,” the Pope said.

“I gave a greeting and nothing more. A greeting is an educated thing to do and does not mean to be mixed up with politics. If someone thinks that to give a greeting means to get mixed up in politics, I think he needs a psychiatrist.”

(This article was updated at 4:46 p.m. Eastern Time to include Pope Francis' comment on the meeting.)

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