(CNN)While U.S. Central Command officials sketched a likely April or May time frame for a looming battle against ISIS in Mosul last week, other military officials tell CNN there are alternative strategies that involve a series of strikes in other locations before an all out attack on Mosul.
The dilemma over when to strike Mosul
At the same time, new Secretary of Defense Ash Carter is making it clear he will not commit quickly to a time table, and wants assurances the Iraqi military is up to the task, a senior U.S. military official said.
Carter wants to ensure military action is not ordered without strong indications Iraqi forces will be successful.
"If we begin this, and it doesn't work, it will be very bad," the official said of an effort to retake Mosul. "The secretary doesn't want it to go faster than the Iraqis are ready to go."
The official also underscored there is "not a broad consensus" among U.S. and Iraqi military and government officials about the tentative April-May launch or the first target city. In fact, some U.S. officials are quietly suggesting that instead of Mosul, which is a densely populated urban area, the first major target for Iraqi forces should be Anbar province and areas west of Baghdad that may not be as militarily challenging.
If Mosul were to be first target, the Pentagon would very quickly have to begin stepped up planning. Topping the to-do list is whether to recommend to President Barack Obama that a small number of U.S. troops be sent in to assist with targeting, which would bring the American troops closer to the front lines. A Mosul attack would also require additional intelligence, supply support and overhead reconnaissance flights increased so a daily list of bombing targets could be established.
The Pentagon and the Central Command, which is running the war, insist that even during a recent briefing for reporters that garnered global attention for mentioning the April-May time frame, it was never an absolute.
"In terms of the Mosul operation, we are still projecting that the shaping for Mosul and the isolation of Mosul is going on now," a Central Command official said during that briefing. "The preparation for the forces that will participate in Mosul is ongoing right now. And the mark on the wall that we are still shooting for is the April-May time frame."
But the official also offered a caveat.
"There are still a lot of things that need to come together. And as we dialogue with our Iraqi counterparts, we want them to go in that time frame, because as you get into Ramadan and the summer and the heat, it becomes problematic if it goes much later than that," the official said. "But by the same token, if they're not ready, if the conditions are not set, if all the equipment that they need is not physically there and they are trained to a degree in which they will be successful, we have not closed the door on continuing to slide that to the right."
A key will be having multi-sectarian units that are sufficiently trained to go to Mosul, rather than all-Shia brigades. The U.S. has already trained 2,500 of the Iraqi troops earmarked for Mosul or other operations, and has another 2,500 undergoing training. Mosul is estimated to require ultimately 20,000 to 25,000 troops but it's not likely they would all deploy at once.
Since the beginning of January, the Defense Department has shipped weapons to the Iraqi armed forces that will be available for use in the upcoming battle for Mosul, a Defense Department official told CNN.
This month the shipments include: 10,000 M-16s rifles, 10,000 M-68 close combat optical scopes to improve on the ground targeting, and 23,000 ammunition magazines, at a cost of about $17 million, according to the official.
"Thousands" of additional helmets and Kevlar vests are being shipped as well, in addition to 250 MRAP mine-resistant vehicles shipped in January and the 232 Hellfire missiles to Iraq sent this year. About 1,500 Hellfire missiles were shipped in 2014.
The official said the shipments were all planned, but the equipment will be in place for Iraqi forces whenever the battle for Mosul begins.