Top Republican senators Friday demanded answers after a military official revealed “detailed operational information” about a looming Iraqi mission to retake Mosul from the Islamic State, saying the disclosure has put the mission at risk.

“Never in our memory can we recall an instance in which our military has knowingly briefed our own war plans to our enemies,” Sens. John McCain, R-Ariz., and Lindsey Graham, R-S.C., said in a letter to President Obama.

“These disclosures not only risk the success of our mission, but could also cost the lives of U.S., Iraqi, and coalition forces.”

The senators asked who was responsible for the briefing, conducted Thursday by a military official, and whether they had White House approval. “Those responsible have jeopardized our national security interests and must be held accountable,” they wrote.

The letter follows criticism in other corners that the military may have revealed too much detail in previewing the operation.

On Thursday, the U.S. military official outlined plans to retake Mosul and said the “shaping” for the battle is currently underway. He said the Iraqi military hopes to begin operations in the “April, May timeframe” with the goal of retaking Mosul before Ramadan begins on June 17.

The official then went a step further and leaked that five Iraqi Army brigades will be used in the fight, as well as several smaller brigades, composing a total force of up to 25,000 Iraqi troops. Three brigades of Kurdish Peshmerga fighters will participate as well. 

But the details, disclosed at the close of a White House summit on combating violent extremism, raised some concerns. 

"That is pretty amazing that that information's out there," retired Gen. Jack Keane, former Army vice chief of staff and a Fox News military analyst, said Friday.  

A current and former military intelligence officer also told Fox News that the decision to publicly announce the plan was counterintuitive because it "telegraphs" the timing and number of units involved. The officers said it would allow Islamic State, also known as ISIS, or ISIL, to prepare for the battle by laying improvised explosive devices.

Both officers questioned whether political considerations on the part of the Obama administration factored into the decision to announce the offensive. 

The Obama administration wasn't the first to discuss plans to retake Mosul, however. Iraqi government leaders previously had talked about the looming offensive, and Defense officials are pushing back on the notion that anything tactical was revealed on Thursday. 

CENTCOM sources also stressed that the briefing on Thursday came from the military, not the White House. 

Keane suggested there should be nothing surprising about the fact that Iraqi forces are looking to retake Mosul before Ramadan. 

"ISIS is not stupid," he said, adding that their fighters already know that Mosul is the key to any counteroffensive and have likely been preparing for weeks. "This is not something new to ISIS."

However, Keane said the details about the force size and other elements were "surprising" to hear. 

ISIS militants overtook Mosul last June, as the group marched across large sections of Iraq and Syria, sending Iraqi forces fleeing. At this point, officials estimate there are between 1,000 to 2,000 ISIS insurgents in the city of Mosul. Military leaders have been talking about retaking the city for some time, but they have said they won't launch the operation until the Iraqi troops are ready.

Included in the force would be a brigade of Iraqi counterterrorism forces who have been trained by U.S. special operations forces. The brigades include roughly 2,000 troops each.

The CENTCOM official said the U.S. will provide military support for the operation, including training, air support, intelligence and surveillance. The official said there has been no decision made yet on whether to send in some U.S. ground troops to help call in airstrikes.

"But by the same token, if they're not ready, if the conditions are not set, if all the equipment they need is not physically there and they (aren't) trained to a degree in which they will be successful, we have not closed the door on continuing to slide that to the right," he said.

The official also revealed for the first time that Qatar has agreed to host a training site for coalition forces to train moderate Syrian rebels who would return to Syria to fight the Islamic State forces there. Other sites are in Turkey, Jordan and Saudi Arabia.