A US Central command official recently told reporters details of the White House's plan to take the Iraqi city of Mosul away from the Islamic State (IS).

The unusual disclosure included the number of troops that would be involved and a time frame for the attack. 

The half-hour teleconference revealed that some 20,000 to 25,000 Iraqi troops currently in training will help carry out the offensive.

In preparation, the official, who spoke under the condition of anonymity, said that the US will continue to provide training, logistical support, "air support, the intel, the ISR (intelligence, surveillance, reconnaissance) – that full range and complement that we have been doing now that has proven very successful when we have the ability to plan, rehearse side-by-side and then execute have been deemed successful."

According to the briefer, the attack will take place between April and May, but that could change based on the soldiers' readiness. 

"If they're not ready, if the conditions are not set, if all the equipment they need isn't physically there to the degree that will be successful, we have not closed the door on continuing to slide [the time frame] to the right," he stated.

The briefer insisted that IS is "in decline," and pointed to the removal of three-quarters of a division of equipment as evidence that IS leader Abu Bakr al-Baghdadi is not making gains. 

"It is no longer there and available to him," the official said, referring to the equipment. 

The terrorist group is having a "very difficult time seizing and holding additional terrain than what it has right now," he asserted. 

An intelligence source called the administration's disclosure "pure lunacy," and revealed that similar decisions have resulted in the militants planting explosive devices near the points of attack.