The so-called Islamic State in Iraq and Syria terrorist group is on the defensive and "their cause is lost"

The so-called Islamic State in Iraq and Syria terrorist group is on the defensive and "their cause is lost," US President Barack Obama said Wednesday after meeting with CIA chiefs and other security officials.

Obama paid a rare visit to CIA headquarters in Virginia to discuss progress of ‘Operation Inherent Resolve’, the 20-month-old U.S.-led failed campaign in Iraq and Syria.

"ISIL is on the defensive, and we are on the offensive," Obama said. "We have momentum, and we intend to keep that momentum."

Obama pointed to alleged US air strikes that killed three senior ISIL leaders and a report this week showing the group's ranks are at their lowest level since 2014.

"In the days and weeks ahead we intend to take out more (leaders.) Every day, ISIL leaders wake up and understand it could be their last," Obama said.

"Their ranks of fighters are estimated to be at the lowest levels in two years and more and more are realizing that their cause is lost," he added.

Obama stressed the importance of ending the five-year war in Syria as key to facilitating a lasting defeat of the ISIL terrorist group.

"So we continue to work for a diplomatic end to this awful conflict," he said.