The Pentagon has offered broad plans to retake Mosul using Kurdish and Iraqi forces to attack the Islamic State-held city from different directions, but there’s a hang-up: Kurdish officials say they are waiting for their Iraqi allies’ to commit to the coming campaign.

“We had [a] discussion to liberate Mosul last year in March…and now we’re in January 2016. So it has been delayed,” Kurdish president Masoud Barzani’s chief of staff Fuad Hussein said in an interview with The Washington Post. “The question is why?…To be honest it has to do with the Iraqis, we need a partner.”

Mosul fell to the Islamic State in June 2014 and has been occupied by the extremist group ever since. While the Pentagon has yet to offer a timeline for the fight to retake it, Hussein said it might be possible this year if Iraqi forces are freed up from fighting in Anbar province in the country’s west.

Hussein added that Kurdish Peshmerga forces have surrounded Mosul from the north, west and east, and that they had left the south for Iraqi forces. Mosul’s southern front, however, is dependent on Iraqi forces fighting in Ramadi, Hussein said. Though some of Ramadi, which fell in May 2015, has been retaken by government troops, there is still heavy fighting throughout the city. Hussein believes that once Iraqi forces are freed up, namely their special operations units known as the Counter Terrorism Service or CTS, only then will the campaign to retake Mosul become a reality.

“That unit has good fighters and are well organized and [has] a lot of experience, so we need them to be with us as partners so that we can jointly with the American help, can liberate Mosul,” said Hussein.

The CTS, stood up in the wake of the American invasion in 2003, was once Iraqi’s premier counter-terror force and assisted in numerous raids against high value targets while U.S. troops were still in the country. After the U.S. withdrawal in 2011 and the rise of the Islamic State, the CTS has become more of a premier light infantry force, and has formed much of the Iraqi Security Forces’ backbone in their recent battles.

But some believe Iraq’s CTS, which has a limited number of fighters, cannot carry the burden of taking back Mosul without significant help from regular Iraqi brigades that as of now, are not ready for that kind of fight.

Senate Armed Services Committee ranking member Jack Reed (D-R.I.) recently returned from a trip to Iraq, Afghanistan, and Djibouti, and said Thursday that winning back Mosul will take more effort than what CTS alone, despite their skill and motivation, can supply.

“When you go up to Mosul, you’re going to need significant forces outside – you can’t just squeeze the city, cut off routes, do that same technique you did in Ramadi – it’s a much bigger city,” Reed said, noting that Iraqi conventional forces’ role in Ramadi was mostly to cut off the city and disrupt ISIS’s lines of communication in and out, so that CTS could fight block-by-block inside.

“I’m sure that CTS will be in the lead [in Mosul],” Reed continued, “but I think you’re going to have to see, in my opinion, Iraqi convention brigades in the fight also in the city.”

On Wednesday, Secretary of Defense Ashton B. Carter told troops stationed at Fort Campbell, Ky. that they would be training Iraqi and Kurdish Peshmerga forces for the coming fight in Mosul, adding that it will not be easy or quick as the advisory role would only offer them a backseat to the coming campaign.

“Our success in Ramadi and north and central Iraq has shown training, advising, and assisting, rather than trying to substitute entirely for local forces is the right approach,” Carter said.

Though training has helped the fledging Iraqi forces and to a certain extent the Kurdish forces, Hussein indicated that more weapons and supplies are needed if the fight to retake Mosul is to be successful. The shipment of ammunition and weapons to Kurdish forces has been a sensitive issue in recent months, as the Kurds have repeatedly asked for the U.S. military to send the supplies directly into Kurdistan instead of going through the Iraqi capital of Baghdad. Sending weapons to autonomous regions, like Kurdistan, is currently not permitted under U.S. law.

Hussein said the Peshmerga need tanks for operations outside the city as well as anti-tank missiles to defeat vehicle-borne improvised explosive devices. To date, the German government has supplied the Kurds with MILAN anti-tank missiles (much like the U.S. TOW system) but Hussein says they need more.