Hossein Amir-Abdollahian, special advisor on international affairs to Iran's speaker of parliament, said he had a meeting with Soleimani and received the evidence while he was working at the foreign ministry.
"He gave me documents and told me to slap them in the face of the West and the UN," Amir-Abdollahian said, according to Press TV.
Soleimani's documents "contained precise information on the geographical position, time and exact details" of US collusion with the terrorists, the official stressed.
For instance, Amir-Abdollahian recalled that while Mosul, Iraq was still under Daesh occupation, "an American A330 [transport plane] landed in Mosul Airport; American generals got off the plane and military equipment was unloaded. At the airport's VIP lounge, the American generals talked with Daesh leaders in Mosul for three hours and 23 minutes and then boarded the plane and returned. What did they bring Daesh? Weapons and equipment it needed and that they had already agreed on."
The official also confirmed earlier reports of US helicopters being used to deliver military equipment to senior Daesh commanders, and evacuating captured leaders. "Later, we found out that the Americans had taken some of those evacuated to northern Afghanistan, some to Libya and others to southern Yemen," he said.evacuating Daesh commanders, and training ex-jihadist militants at the Al Hasakah refugee camp in northeastern Syria.
Last week, Iran's Foreign Minister charged the US of regularly evacuating militants out of Syria and Iraq. These claims have been echoed by former Afghan President Hamid Karzai, who claimed that Daesh was a "tool" used by Washington in Afghanistan to pursue its broader goals in the region.