BAGHDAD — Iraq’s government is holding off on waging an all-out offensive to retake two key cities from Al Qaeda 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 Qaeda-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 United States invaded Iraq in 2003 and withdrew in 2011. Both countries tried but failed to negotiate plans to keep at least several thousand US 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 US concerns about Al Qaeda-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 Qaeda 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.
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.
Tribal leaders in Fallujah have warned Al Qaeda 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.