In a phone conversation late on Friday, the two reaffirmed their commitment to mutual cooperation to ensure the end of hostilities in Syria as soon as possible.
Engdahl, for his part, said that the current events in Syria should, first of all, be seen as a fierce struggle for control of the country's oil resources.
"It's a fight for the oil, it's not a fight not for the religious principles. Essentially, it's a game for control over Syria's oil riches, nothing more than that," Engdahl pointed out.
He remained downbeat about the future of the Syria peace talks, saying that "everybody is lying to everybody", with the United States, for example, already discussing a possible partition of Syria in the event that the talks come to a standstill.
The latest round, more than a month after de Mistura suspended the previous sit-down, comes as Russia and the United States reached an agreement on the ceasefire in Syria that took effect on February 27.
The cessation of hostilities is generally holding across the country despite minor reported violations.