The Obama administration faces a tough decision on whether to provide more arms to Iraq’s government.

Some arms have already fallen into the hands of the Islamic State of Iraq and Syria (ISIS), an al Qaeda-linked group that has taken over the Iraqi cities Mosul and Tikrit and is advancing on Baghdad.

{mosads}The Pentagon has acknowledged that the group sized some U.S. equipment and vehicles as the Iraqi army folded in front of it.

“They’re driving some of these vehicles, they’re in possession of some of this stuff, but I’d be loathe to tell you that we actually have a really solid sense of what they’ve got,” Pentagon Press Secretary Rear Adm. John Kirby told reporters Friday. 

“We don’t have a perfect indication of the captured equipment that they have,” he said. 

The worry is that more arms could end up with the group if it is able to take over Baghdad.

“We don’t want to be rushing equipment that will end up behind enemy lines,” said Jeffrey White, a defense fellow at the Washington Institute. 

The State Department expressed concern Friday that arms had fallen into the hands of militants, but did not say what this might mean for future arms sales or loans.

“We are certainly concerned that the fact that [ISIS] has gotten its hands on so many weapons, both in Syria and Iraq, is a very serious security concern for both countries,” State Department Deputy Press Secretary Marie Harf told reporters Friday.

Harf said State has discussed the possibility of additional arms sent to Iraq falling into ISIS’s hands.

“I know that’s a concern people have raised,” she said. “But we do believe that there is a path forward here working with the Iraqi army to bolster their capacity. But it needs to be matched by a political commitment to bring the country back together to do so. So we know it’s a challenge, certainly.”

Michael Knights, a former adviser to the Iraqi government who is now also a fellow at the Washington Institute, said that 60 out of 243 Iraqi army battalions and their equipment “can’t be accounted for” after those forces fled Mosul and abandoned their gear. 

The seized equipment includes everything from hundreds of Humvees, tanks and infantry fighting vehicles to mortars, small arms and ammunition, White said.

He said some equipment has already shown up in neighboring Syria, where ISIS forces have established a safe haven. 

There is pressure on the administration to do something in response to the rise of militants in Iraq and Syria. Their lightning-like advance in Iraq has taken officials by surprise, and sparked worries of a terrorist safe haven from where the U.S. could be attacked.

The militants have fought Syrian President Bashar Assad’s forces, but have also turned against U.S.-backed moderate opposition forces in Syria.

One reason the administration did not provide opposition forces in Syria with lethal aid for months was the fear it would end up with groups such as ISIS.

The U.S. had promised Iraq more advanced weaponry.

After ISIS took over the Iraqi city of Fallujah earlier this year, the U.S. promised Iraqi officials it would speed up deliveries of attack helicopters, surveillance drones and Hellfire missiles, to help fend off the very type of jihadist siege Baghdad could be facing.

White said this may no longer be a good idea. 

“The obvious answer is yes, we should rush all that equipment over there as quickly as possible,” White said. “But we need to assess what’s going on, whether Iraqi forces can recover from this and make a stand.” 

The U.S. has plans to supply $15 billion worth in military equipment to Iraq, including F-16 fighter jets, and is scheduled to deliver the first batch of 24 Apache attack helicopter as early as this summer.

Defense officials on Friday said there are no plans to stop the deliveries, but at the same time say they are contingent upon whether they will be secure. 

“We don’t even have a date set yet for Apache delivery,” one defense official said on background, adding, ”Security is always a concern in moving forward with [foreign military sales] that involve advanced weapons systems.”

At the same time, the official pushed back against the notion that the U.S. “has to speak to the custody of every piece of military equipment given to Iraqi forces.” 

“This is Iraqi equipment,” the official said.