Smoke rises after a bomb attack in the city of Ramadi, May 15, 2015. Islamic State militants raised their black flag over the local government headquarters in the Iraqi city of Ramadi on Friday and claimed victory through mosque loudspeakers after overrunning most of the western provincial capital. If Ramadi were to fall it would be the first major city seized by the insurgents in Iraq since security forces and paramilitary groups began pushing them back last year. [Photo/Agencies]

WASHINGTON - Despite major new setbacks in Iraq, the US military command leading the fight against Islamic State militants insisted Friday that its strategy is working and that the militants' takeover of a key oil refinery and a government compound are fleeting gains feeding an IS propaganda machine.

"We believe across Iraq and Syria that Daesh is losing and remains on the defensive," said Marine Brig. Gen. Thomas D. Weidley, chief of staff for Combined Joint Task Force Operation Inherent Resolve, the name of the international campaign fighting IS. "Daesh" is the Arabic acronym for the militant group that swept into Iraq from Syria last June and swiftly took control of much of Iraq's north and west.

Even as Weidley spoke to reporters by phone from his headquarters in Kuwait, IS militants were defying his description of them as a force on defense. Iraqi officials said IS fighters had captured the main government compound in Ramadi, the capital of battle-scarred Anbar province. Other officials said they had gained substantial control over the Beiji oil refinery, a strategically important prize in the battle for Iraq's future and a potential source of millions of dollars in income for the militants.

The battle to push IS out of Mosul, the largest city in northern Iraq, which some had hoped would begin this spring, now seems a more distant goal.

The Pentagon insists that it knew when it began a bombing campaign in Iraq in August 2014 that it could take years to force the Islamic State group out of the country, and while the militants have conceded some ground in recent months, including the northern city of Tikrit, they have proven remarkably resilient.

Just over 3,000 US troops are training and advising Iraqi forces and providing protection for US forces and facilities. Weidley said there is no move afoot to either expand the US presence or ask the Obama administration for authority to put US troops close to the front lines of combat.

Weidley appeared to be pressing his own "information campaign" designed to counter the militants' message of defiance. While conceding the militants' were managing "episodic control" of certain terrain in Iraq, he insisted their advances were minor and unsustainable.

The State Department offered a similar assessment. "There will be good days and bad days in Iraq," State Department spokesman Jeff Rathke said. "ISIL is trying to make today a bad day in Ramadi. We've said all along we see this as a long-term fight."

Weidley said IS fighters had launched a complex attack Friday on Ramadi as part of an effort to "feed their information and propaganda apparatus." He called Ramadi a "critical city" but said he could not confirm how much of the city had been lost to IS on Friday or what percentage remains in Iraqi control. He said his command had seen Islamic State social media postings of photos that depict a successful Ramadi offensive.

"This is similar to the (techniques) they've used in the past where they've conducted attacks trying to gain social media gains by taking photos and documenting small-term gains and then using it for propaganda purposes," Weidley said, adding that IS was inflating the importance of its success.

"We've seen similar attacks in Ramadi over the last several months for which the ISF (Iraqi security forces) have been able to repel, and we see this one being similar to those," he said, adding that the US is confident the Iraqi government will be able to take back the terrain it has lost in Ramadi.

In Ramadi, Iraqi troops were forced to withdraw during an attack in which three suicide car bombs killed at least 10 people and wounded dozens more, said Mayor Dalaf al-Kubaisi. The mayor said the militants raised their black flag over the captured government compound, which houses provincial and municipal government offices.