U.S. calls fall of Ramadi 'very serious'

Dempsey also said the U.S. and Iraq are conducting a review to determine exactly what did happen in Ramadi.

In contrast, the State Department official took a darker view of the fall of the key Iraqi city, the capital of Iraq's western Anbar Province.

"This is a very serious situation. No one is kidding themselves about that," the official said.

The assessment also runs somewhat counter to that offered by Dempsey back in April.

"The city itself it's not symbolic in any way," Dempsey said. "I would much rather that Ramadi not fall, but it won't be the end of a campaign."

The State Department official said the fight for Ramadi lasted over 18 months, with Iraqi forces fighting off ISIS advances while suffering casualties in the thousands.

ISIS had seized parts of the city during that time but it wasn't until the Iraqi forces attempted to reinforce their troops that their losses become too significant to continue holding the city.

The State Department official said the major turning point in Ramadi happened after ISIS launched more than 30 suicide attacks, 10 of which packed explosive power comparable to the Oklahoma City bombing, which wrought devastation on the central government district.

However, the Department of Defense reports a different number and scale of suicide bombings. Major Curtis Kellogg of U.S. Central Command said the Pentagon's intelligence only indicates that there were eight bombings in Ramadi and none comparable with Oklahoma City.

The intensity of the bombings is a critical point as the State Department official cited their frequency and intensity as one of the key reasons Iraqi forces had to fall back. The State Department did say Thursday it's hard to quantify the exact number of bombings given the chaos on the ground.

The State Department official said the Obama administration is pleased with the response so far by the Iraqi government. The Iraqi plan going forward is to recruit more Iraqi military forces, reorganize the police and national guard and give provincial governors more autonomy nationwide as they may have a clearer picture of what's going on in their area as compared to Baghdad.

But Republican Arizona Sen. John McCain said that after months of coalition bombardment of ISIS targets in both Iraq and Syria, President Barack Obama needs to reevaluate the whole strategy in the fight against ISIS, including committing more troops.

"We're not doing enough of anything. We need to train, we need to equip, we need to have boots on the ground for forward air controllers," McCain said. "There has to be total reevaluation of our abysmal failure and the consequences of it."

The Iraqis will also be relying on some Sunni tribal fighters and Iranian backed Shiite militias. There's concern in some quarters that could stir sectarian tension and that the Iranians will be filling the area's power vacuums.

But the State Department official stressed it's only natural for Iraq and Iran to have a relationship and that, as long as Iran respects Iraq's sovereignty, the U.S. has no issue with the country being involved.

Still, the U.S. official cautioned Iran's role may be a bit overblown.

"Iran always wants to seem like it's an indispensable player in Iraq," he said.

Though ISIS has seized Ramadi, coalition air forces still control the skies. The coalition continues to monitor for signs of ISIS movement in the city and there have been several airstrikes since the weekend.

The official also admitted that the fall of Ramadi would delay the attempted retaking of Mosul later in the year, a city whose capture was evaluated as a bigger setback.

He said ISIS has thousands of fighters from more than 100 countries, more than double what the Soviets faced in Afghanistan in the 1980s.

The coalition fight to crush ISIS could end up taking years. "We've never seen something like this," he said.