A U.S.-backed military offensive against Islamic State fighters faltered in its first week as several hundred militants entrenched in the provincial capital of Ramadi withstood punishing airstrikes and held off a far-larger force of Iraqi ground troops, senior U.S. and coalition commanders said Saturday.
The slow going in what officials portray as a major test of efforts to bring Iraq's fractured security forces into a common front against the Sunni Muslim extremists comes as a truck bomb late Friday killed more than 100 people, including women and children, in a mostly Shiite Muslim market town about 35 miles north of Baghdad.
The explosion in Khan Bani Saad, one of the deadliest since U.S. combat troops withdrew from Iraq in December 2011, caught shoppers out for the Eid al-Fitr celebration that marks the end of the holy month of Ramadan. Islamic State claimed responsibility, posting grisly pictures online of bodies and wreckage-strewn streets, and saying the attack was aimed at government-allied Shiite militia fighters.
U.S. and Iraqi leaders rushed to condemn the bombing, which the White House said "purposefully and viciously targeted Iraqi civilians" celebrating a religious holiday.
The push by pro-government forces to retake Ramadi, which fell to the militants in May, includes about 10,000 members of the Iraqi army, federal police and Shiite militias, and Sunni tribal fighters.
But they have struggled to gain ground against heavy resistance, including hundreds of booby traps and other defenses built by a small but capable force of 250 to 350 Islamic State fighters believed to be holed up in the city, about 60 miles west of Baghdad.
"Progress has been steady but difficult," Brig. James Learmont, a British senior officer detailed to the U.S. Army's 82nd Airborne Division as deputy commander, said Saturday. "They've had time to prepare defenses."
U.S. and other coalition warplanes pummeled militant positions in the city and its outskirts with 29 airstrikes on July 12, the first night of the offensive. But they sharply reduced the air attacks as it became more difficult to find viable targets.
Fighting also was reported near Fallouja, another major Sunni-dominated city in the Euphrates River valley that the militants captured in January 2014. The assault involves a large-scale deployment of government-allied Shiite militias against a heavily defended militant stronghold and urban center, and Iraqi officials predicted a difficult fight ahead.
Fallouja is "like a wasps' nest," Mowaffak Rubaie, Iraq's former national security advisor and now a member of the parliament in Baghdad, said by email in recent days.
A government offensive in Anbar this year petered out without success, and it wasn't clear whether the use of Shiite irregular troops would succeed or lead to greater sectarian conflict. Anbar stretches from the Syrian, Jordanian and Saudi Arabian borders to the edge of Baghdad, and saw the heaviest U.S. casualties during the eight-year U.S.-led American war in Iraq.
The abrupt government defeat in Ramadi in May forced the White House to reassess its strategy for pushing Islamic State back, and President Obama has offered only guarded assessments of the seesawing progress.
At a White House news conference Wednesday, Obama said his goals for the end of his term in 2017 include ensuring "that we are on track to defeat [Islamic State], that they are much more contained and we're moving in the right direction there."
The Obama administration has sought to dislodge the militants since August with a strategy based on airstrikes, intelligence sharing and training and arming Iraqi government troops, Sunni tribal fighters and Kurdish forces under control of Prime Minister Haider Abadi's government in Baghdad.
About 3,500 U.S. military personnel are deployed at a few bases in the country, including several hundred at a newly opened training camp between Ramadi and Fallouja, but they are barred from taking part in ground combat operations.
U.S. and Iraqi critics have urged the White House to authorize a more direct American role in the war, including putting U.S. advisors into combat with Iraqi units and assigning forward air controllers to front lines to help direct airstrikes.
Gen. Martin Dempsey, the outgoing chairman of the Joint Chiefs, who visited Baghdad on Saturday, questioned top commanders about whether the U.S. should get directly involved in ground combat.
"I asked, 'Are we at that point?'" Dempsey said. "And they said, 'No, we are not at that point.'"
The commanders confirmed reports that efforts to train Iraqi troops are behind schedule. Coalition forces can train as many as 24,000 Iraqi troops a year, but only 9,700 have gone through the training this year.
"We have the capacity to train more," said Learmont, the British brigadier. He said the shortfall was the result of Iraq's inability "to provide the trainees while constantly fighting" Islamic State on multiple fronts in northern, western and central Iraq.
Dempsey said Iraq's Shiite-led government is rife with sectarian divisions and disagreements about who should take the lead in trying to retake Sunni-dominated Anbar, Iraq's regular army or the Popular Mobilization Units, the mostly Shiite militias that are backed by Iran.
If Iraqi security forces fail to recapture Ramadi, or rely heavily on the Shiite militias, it could strengthen those in the government who support the militias and raise new rivals for Abadi, a U.S.-backed leader who has sought to limit the militias' role.
"There is a competition within the government of Iraq about which security forces will be dominant," Dempsey said.
Shiite militias initially took the lead in trying to retake Tikrit this year, but when a monthlong offensive stalled they were ordered to pull back so U.S. warplanes and Iraqi troops could move in. Human rights groups later accused some Shiite troops of extrajudicial killings and other sectarian abuses against the city's Sunni residents.
Shiite militias are widely regarded as among Iraq's most effective armed forces. The fighters are highly motivated to confront Islamic State, which regards Shiites as heretics and regularly executes Shiite captives.
U.S. officials, who won't directly coordinate with the militias, have pressed Abadi's government to recruit Sunni Arab tribes to handle much of the fighting, and they said the effort is showing some progress.
The U.S. has also used the new training base in Anbar to reach out to the tribes, hoping to replicate a strategy that proved successful during the U.S. troop buildup in 2007 that helped quell the then-rampant Sunni insurgency, at least for a while.
Deliveries of heavy weapons by the U.S. and other allies, including more than 2,000 AT-4 antitank missiles, have increased in recent weeks and have been distributed to Iraqi army units. The Iraqi government also took delivery of its first four F-16 fighter jets, which it said would be used in the Anbar offensives.
Cloud reported from Baghdad and Hennigan from Washington. Special correspondent Nabih Bulos in Beirut contributed to this report.