The U.S. military’s goal to retake Iraq’s second largest city from the self-proclaimed Islamic State has been pushed back several months at least, defense officials told The Daily Beast. That’s a major shift for the Pentagon, which recently announced that the first major ground offensive in the war against ISIS could come in the next few weeks.

Defense officials once hoped that Iraqi troops could move into Mosul by the Spring and reclaim the city from ISIS. Now, those officials say, Fall is more realistic. And even that date was tenuous.

“It is an Iraqi decision but we don’t want to do anything until they are ready and can win decisively,” a military official explained to the Daily Beast. “They cannot now.”

It’s another sign that the U.S.-led campaign against ISIS isn’t going nearly as smoothly as the American government had hoped. At the Pentagon Friday, Defense Department spokesman Rear Adm. John Kirby shied away from any kind of timeline, saying: “I can’t put a date certain…nor say April is out.”

Rather, he suggested that the Iraqi forces were not imminently ready for such an offensive.

“I don’t think we are there yet,” Kirby said. “There are gaps and seams that need to be closed.”

A group within U.S. government pushed for a Spring offensive out of concern that the next opportunity to launch such a campaign would not be until the Fall. But these policymakers appeared to have been trumped by those fearing that Iraqi forces are nowhere near ready.

The shift away from the Spring began in the last few days, in part because officials could not agree publicly about whether the Iraqi forces would be ready for the fight. Defense Intelligence Agency Director Lt. Gen. Vincent Stewart told the Senate Armed Services Committee Thursday that it would be “six to nine months, best estimate,” before Iraqi forces could be able to launch a major counteroffensive against ISIS.

“When we talk about the six to nine months additional training, it is to deal with an urban fight, which is very, very different, very complex, requires a great deal of skill, great deal of precision to be successful,” Stewart said.

The timeline is expected to come up publicly again Tuesday when Secretary of Defense Ashton Carter and Chairman of the Joint Chiefs of Staff Army Gen. Martin Dempsey testify before the Senate Armed Services Committee.

Dempsey isn’t expected to address the timeline for such an offensive directly. Rather, he’ll argue against the potential “rush to failure,” as one defense official explained.

Earlier this month, a U.S. Central Command official gave a briefing to reporters saying that Iraqi forces could be ready by April or May to launch an offensive to take back the northern Iraqi city of Mosul from ISIS, where the group is entrenched. ISIS has controlled Mosul since June, when Iraqi troops fled their posts as ISIS forces stormed the city.

The proposed offensive would take as many as 25,000 troops assigned to at least eight Iraqi brigades, the CENTCOM official said on the condition of anonymity. The forces would seek to root out 2,000 ISIS fighters, he added.

U.S. forces would support that campaign by the air, but the CENTCOM official did not offer any specifics.

Even before it was delivered, the CENTCOM briefing set off a flurry of criticism in both Iraq and the United States. In the weeks leading up to the announcement, Iraqi leaders said their troops would not be prepared to striker until the fall, at the earliest. Iraq’s two best divisions now protect the capital and there did not appear to be a sufficient force to move in and replace them there during a potential offensive.

There were sectarian considerations, as well. The Iraqi divisions who would likely lead such a campaign are majority Shiite forces; Mosul is a Sunni-dominated town and such sectarian delineations are important to all involved. Many worried that Sunnis in both Iraq and the broader Arab world would not accept a Shiite-dominated military force leading the campaign.

Still others were angry that the U.S. military decided to telegraph the mission and the details of it. Republican Sens. John McCain and Lindsey Graham blasted the announcement in a letter to President Obama, calling the disclosure a risk to “the success of our mission, but could also cost the lives of U.S., Iraqi, and coalition forces.”

Since December, when U.S. officials first suggested a spring timeline, the Iraqi government repeatedly pushed back publicly, saying its forces were not ready. And yet U.S. officials kept suggesting such a campaign was possible. The CENTCOM briefing outraged many in Baghdad who felt pressured. In a televised address last week, Iraqi Defense Minister Khaled Obeidi would not confirm the proposed timeline, but rather rejected the U.S. decision to name specific months for an operation.

“This is urban warfare and we have civilian populations. It is very important to take time and accuracy in setting the plan for this battle,” Obeidi said.

All the while, there were inside the Pentagon that launching a plan too soon could have long term adverse affects on their seven-month air campaign against ISIS.

CENTCOM officials appeared eager to launch the campaign in anticipation of the summer and holy month of Ramadan, when troops would be fasting from sunrise and sunset, making such an offensive all but impossible.

But as criticism of that plan mounted, defense officials increasingly began stressing readiness and not timelines. Rather than an American-pushed spring offensive, officials stressed, it was an Iraqi-led operation that would be decided by the government there.

“we’ve said that the Mosul offensive could occur as early as spring, but—and we offered this caveat a number of times during the briefing—the Mosul op will be conducted by the Iraqis with our support and it won’t happen until they’re ready and we’re certain that they will be successful,” said Air Force Col. Patrick Ryder, a CENTCOM spokesman, in response to a Daily Beast query.

U.S. politicians also spoke more about the military force and less about the timeline.

“I’d be very surprised if they would be ready,” California Rep. Adam Schiff (D) told CNN Thursday. “I wouldn’t want to see the Iraqis go before they are ready.”

The battle for Mosul would be the most intense of the fight against ISIS. At its peak, the city was home to 1.5 million people and ISIS has spent months building barriers and digging trenches to protect the city. Indeed, ISIS has said it considers Mosul a key part of its proposed Islamic caliphate, one that it is prepared to defend.

That said should it lose control of the city, it would be all but impossible for the group to retain its grip on nearly a quarter of Iraq as it would lose thousands of fighters and millions of dollars in procured military equipment, as well much needed momentum.