BAGHDAD -- Iraq's government is holding off on waging an all-out offensive to retake two key cities from al-Qaida because of fears that civilian casualties could incite Sunni anger and push moderate tribal leaders to side with the extremists, analysts and military officials said Thursday.
More violence flared in Baghdad, where a suicide bomber killed 21 people at an army recruiting center in a clear effort to demoralize the military.
Al-Qaida-linked fighters overran parts of the cities of Fallujah and Ramadi in Sunni-dominated Anbar province last week, seizing control of police stations and military posts, freeing prisoners and setting up their own checkpoints.
The United States, whose troops fought bloody battles in the cities, has ruled out sending its troops back in, but has been delivering missiles to bolster Iraqi forces. It is expediting shipments of more American-made missiles and 10 surveillance drones, but those may not arrive for weeks.
The U.S. invaded Iraq in 2003 and withdrew in 2011. Both countries tried but failed to negotiate plans to keep at least several thousand U.S. forces in Iraq beyond the deadline to maintain security.
Vice President Joe Biden has spoken to Prime Minister Nouri al-Maliki twice this week, voicing support for his government's efforts to regain control of the cities and urging him to continue talks with local, tribal and national leaders.
Iran, too, is watching the unrest with alarm, since it shares U.S. concerns about al-Qaida-linked militants taking firmer root in its neighbor. It has offered to supply military equipment and advisers should Baghdad ask.
Iranian President Hassan Rouhani told his Russian counterpart, Vladimir Putin, in a telephone call that the campaign against al-Qaida should intensify, the official IRNA news agency reported.
"If terrorism is not suppressed and if military support to terrorist groups by some countries is continued, the security of the region and the world will be jeopardized," he said in an apparent reference to Saudi Arabia and other Sunni-led states. "In confronting terrorism, the ideological and financial roots of the terrorism also should be destroyed."
Iraqi troops have clashed with the fighters mainly on the outskirts of the cities and carried out occasional airstrikes against their positions. But they have held off launching major offensives to retake either.
One senior intelligence official said the reason for the delay was to avoid civilian casualties.
"We have enough soldiers, but we are waiting for the American drones and missiles. These weapons will have a big role in the coming battle," the official said.
Baghdad-based political analyst Hadi Jalo agreed that concerns over civilian safety might explain why the government has not launched a major offensive.
"The killing of civilian victims will drive more people looking for revenge ... to join al-Qaida. If women and children are killed in any possible military action against Fallujah, al-Maliki will lose the support of moderate Sunnis," he said.
A military commander in Anbar said there are other concerns beyond residents' safety.
"The battle in Anbar ... is a kind of a guerrilla war, and the Iraqi army and police do not have experience in these kinds of wars," the commander said. He added that snipers operating out of residential areas appear to be "peaceful civilians" by day and take up new positions at night.
The military and intelligence officials both spoke on condition of anonymity because they were not allowed to discuss the operation publicly.
Tribal leaders in Fallujah, 40 miles (65 kilometers) west of Baghdad, have warned al-Qaida fighters there to leave to avoid a military showdown, and there were signs that residents were trying to restore a sense of normal life, however precarious.
"State offices and banks have opened their doors. Offices have started giving salaries to civil servants, and policemen have started working as usual," said resident Rashid al-Dulaimi.
But several al-Qaida fighters and residents who had taken up arms to prevent Iraqi forces from reasserting control over Fallujah remained mainly on its outskirts Thursday and outside strategic locations such as banks, witnesses said.
A number of police stations that were overrun by al-Qaida fighters last week have been torched and largely abandoned.
Al-Maliki hinted at a possible pardon for militants who abandon the fight, saying Wednesday that his government will "open a new page to settle their cases so that they won't be fuel for the war that is led by al-Qaida." It is unclear if this represented a formal amnesty offer, however, and hard-line Sunni fighters are unlikely to have faith in the Shiite-led government's assurances.
Human Rights Watch said Iraqi forces appear to have used mortar fire indiscriminately in civilian areas in recent days to try to dislodge militants in Anbar and that some neighborhoods were targeted with mortar shells and gunfire even though there was no sign of an al-Qaida presence there.
The New York-based group said its allegations were based on multiple accounts provided by Anbar residents.
It also warned that a government blockade of Ramadi and Fallujah is limiting civilian access to food, water and fuel, and that "unlawful methods of fighting by all sides" has caused civilian casualties and major property damage.
Several approaches to Fallujah have been blocked by Iraqi troops, and only families with children were being allowed to leave with "extreme difficulty" through two checkpoints, the rights group said. It added that single men were being denied exit from the city.
"Civilians have been caught in the middle in Anbar, and the government appears to be doing nothing to protect them," said the group's Mideast director, Sarah Leah Whitson.
Iraqi government officials could not immediately be reached for comment to respond to the rights group's allegations.
The warning came a day after the U.N. and the International Committee of the Red Cross voiced concerns about growing humanitarian threats in the area as food and water supplies start to run out.
Emergency shipments of food, water, blankets and other essential items have begun reaching families displaced by the fighting, the U.N. said. Some of the initial supplies were delivered to families left stranded in schools and mosques in Fallujah.
More than 11,000 families have been displaced by the fighting, according to U.N. records.
The Baghdad bomber detonated his explosives outside the recruiting center in the capital's central Allawi neighborhood in the morning as volunteers waited to register inside, a police official said.
In addition to the 21 dead, at least 35 people were wounded, he added, and a hospital official confirmed the casualty numbers. Both officials spoke on condition of anonymity because they were not authorized to talk to the media.
There was no immediate claim of responsibility, but suicide attacks are the hallmark of al-Qaida's Iraq branch, known as the Islamic State of Iraq and the Levant.
The recruiting center attack appears to be in retaliation for the military's response to the insurgency and an effort to dissuade potential new recruits from bolstering the Iraqi army's ranks.
It followed an attack late Wednesday by gunmen who struck at army barracks in Diyala province, north of Baghdad, killing at least 12 soldiers.
Al-Qaida militants, emboldened by their gains in the civil war in neighboring Syria, have sought to position themselves as the champions of Iraq's disenchanted Sunnis against the Shiite-led government, even though major Sunni tribes in Anbar and elsewhere oppose the group's extremist ideology and are, in some cases, fighting against it.
Sectarian tensions have been rising for months in the province as Sunnis protested what they perceive as discrimination and random arrests by the Shiite-led central government. Violence spiked after the Dec. 28 arrest of a Sunni lawmaker sought on terrorism charges and the government's dismantling of a year-old Sunni protest camp in Ramadi, the provincial capital.
-- Schreck reported from Dubai, United Arab Emirates. Associated Press writer Sameer N. Yacoub contributed from Baghdad.