BAGHDAD: After retaking most of the key city of Ramadi from ISIS militants, Iraqi leaders say they are setting their sights on an even bigger prize: Mosul.

Iraqi forces have driven ISIS jihadists out of the heart of Ramadi, which the Sunni extremist group seized in May in a humiliating setback for the Iraqi government and the U.S.-led coalition that's backing it.

Significant pockets of ISIS resistance remain in Ramadi, still controlling as much as 25% of it as of Tuesday, local tribal leaders said. But that didn't stop Iraqi Prime Minister Haider al-Abadi from visiting the shattered city and raising the national flag.

Next year "will be the year we drive ISIS out of Iraq," he declared.

With efforts to finish clearing ISIS out of Ramadi still expected to take weeks, it seemed like a bold statement, especially in light of the militants' habit of hiding among local populations and booby-trapping territory they give up.

Mosul is different than Ramadi     

Reclaiming Mosul, the country's second largest city, will be a crucial step in trying to achieve Abadi's ambitious goal.

Mosul, a city of more than 1 million people about 400 kilometers (250 miles) north of Baghdad, fell to ISIS in June 2014 as Iraqi security forces fled en masse in a stunning defeat that underscored the Islamic militant group's rapidly expanding menace.

U.S. officials appear more cautious than their jubilant Iraqi counterparts about the scale of the challenge.

"Mosul is different than Ramadi, it's a big, big, big city and it is going to take a lot of effort," said Col. Steve Warren, the spokesman for the U.S.-led coalition fighting ISIS. "It's going to take more training, it's going to take more equipment and it's going to take patience."

Squeezing ISIS out of Fallujah

He expressed optimism, though, that Iraqi forces would be able to hold onto their gains in Ramadi and progress in efforts to retake nearby Fallujah, another important city in the predominantly Sunni Muslim Anbar province.

"The fight for Fallujah is ongoing. Right now the Iraqi Security Forces are approaching Fallujah from three directions," he said.

"Essentially, they encircle the city, almost like a boa constrictor, and they will then squeeze in closer and closer into that city until eventually they are able to finally clear it, as we saw in Ramadi," Warren told reporters.

Fallujah saw some of the harshest fighting between U.S. forces and ISIS' predecessor, al Qaeda in Iraq, back in 2004. And it may prove to be a rallying point for jihadists once again.

Rebuilding a bombed out city

The Iraqi military's success in Ramadi was notable for not relying on the Iranian-backed Shiite militias that were key to retaking the city of Tikrit from ISIS in March.

"There were no Shia militias involved in this operation for Ramadi," Warren said.

That approach was seen as vital to avoiding an escalation of the sectarian tensions that have helped ISIS' Sunni extremism gain such a stubborn foothold in parts of Iraq.

Iraq's Shiite-dominated government in Baghdad is hoping that by bringing local Sunni tribal leaders in Anbar province into the political process they can help prevent Ramadi and other areas from slipping back into ISIS' grasp.

Local officials will face a raft of challenges rebuilding the ruined city, where the U.S.-led coalition says it has carried out more than 630 airstrikes in the campaign to retake it from ISIS since July.

The city, which tens of thousands of people fled during months of fighting, will need to restore basic infrastructure like electricity and running water as well as its residents' sense of security.

Courtesy CNN