Story highlights Iran's elite Quds Force is training, advising and supporting Iraqi Shia militias in their fight against ISIS.

Iranian officials say they would like better cooperation with the U.S., but say trust between the nations is lacking

Tehran, Iran (CNN) The Basij is a militia made up of fighters loyal to Iran's religious leaders; their mission is to protect the country's Islamic order.

To do that, they will go to any lengths necessary, including -- they say -- taking on ISIS.

"We all are prepared to go and destroy ISIS totally," one Basij commander told CNN. "If our Imam, our Supreme Leader orders us, we will destroy ISIS."

The commander says that, so far, the Basij has not been caught up in the fight against the feared Islamic extremists currently waging war in parts of Iraq and Syria.

But Iran's elite Revolutionary Guard's Quds Force, led by General Qassem Suleimani, is already training, advising and supporting Iraqi Shia militias in their fight against ISIS.