BAGHDAD - Just last month Shi'ite Prime Minister Haider al-Abadi visited the Habbaniya military base in Iraq's Sunni heartland hoping to fire up pro-government fighters seen as critical in the battle against Islamic State militants.
But the group's seizure of provincial capital Ramadi in Anbar has forced the man once seen as the best hope for healing sectarian divisions to try perhaps the most perilous approach – deploying Shi'ite militias long seen as a destabilizing force.
On Monday, a column of 3,000 Shi'ite militia fighters arrived at Habbaniya near Ramadi as Baghdad moved to retake the western city that had fallen in the biggest defeat for the government since mid-2014.
That raised the prospect of an escalation of sectarian bloodletting in Iraq, still struggling to find a formula for stability four years after the last U.S. troops withdrew.
Shi'ite militias say they are focused on ridding Iraq of Islamic State, the ultra-hardline group that has also seized large parts of neighboring Syria.
Many Sunnis say the militias kidnap and kill members of their sect at will because the government is unwilling or too weak to rein them in, allegations they deny.
Loss of Ramadi
Abadi ran out of choices as the Islamic State group – which had already seized large parts of northern and western Iraq – took over Ramadi.
The Iraqi armed forces have yet to prove they can take on Islamic State fighters without the help of Shi'ite militias backed by Iran, a regional power with vast influence over Abadi's government.
When Abadi replaced polarizing figure Nouri al-Maliki as prime minister in 2014, he seemed optimistic that sectarian divisions tearing the country apart could heal.
His government repeatedly pledged to equip and train Anbar's Sunni tribes with a view to replicating the "Awakening" model applied during the surge of 2006-07, when U.S. Marines turned the tide against al-Qaida – forerunners of the Islamic State group.
But hopes for a new alliance with the Sunni tribes faded even as massacres of hundreds of their members by the Islamic State group injected a greater sense of urgency.
The Islamic State Ramadi advance has triggered more alarm bells even among Sunni tribes who have long been suspicious of Hashid Shaabi, an umbrella group for Shi'ite militias, forcing Abadi to pursue the only viable option.
Dependent on Shi'ite militias
That leaves Iran in a position to keep calling the shots as Abadi's government becomes more dependent on its powerful Shi'ite militia allies, analyst say.
"I don't think Abadi is quite so damagingly anti-Sunni as Nouri al-Maliki was, but I just don't think he has a choice at this point," said Charles Lister, visiting Fellow at the Brookings Doha Center.
"When you hear the Anbar provincial council calling on the Hashid Shaabi to join the fight in Anbar, that essentially gives him the excuse that perhaps he so desperately needed to actually deploy his last attempt, which was to put these militias into play."
Lister predicts the Shi'ite militias will gain a much bigger role in the next few weeks as Abadi's government faces the prospect of an ever more ambitious Islamic State group, which has vowed to reach Baghdad.
The capital is unlikely to fall any time soon because of a large presence of Shi'ite militias and special forces.
But Islamic State's presence in nearby Ramadi raises new questions about the fate of Iraq, which has benefited from U.S. airstrikes on Islamic State but still faces a grave security threat from the militants.
The deployment of Shi'ite militias near Ramadi is likely to deepen divisions in Iraq, even among Sunnis, the minority sect that dominated under Saddam Hussein but which has now become deeply resentful of the Shi'ite-led government.
While some desperate tribal leaders welcomed the Shi'ite militias, others are now more sceptical that Abadi ever offered a change from Maliki.
Sheikh Ali Hammad, from the Anbar town of Falluja, accused the government of deliberately allowing Ramadi to fall to provide a pretext for deployment of Shi'ite militias to "exterminate the Sunnis."
"They wanted to us reach this point. The people and the provincial council were forced to accept the entrance of the Hashid because they didn't give weapons to the Sunnis," Hammad said.
"What has he [Abadi] done for us? Yes, he is different in style, and doesn't talk in a sectarian way, but we haven't seen anything concrete to conclude he is different from Maliki. Abadi doesn't rule Baghdad; the militias rule," he added.
Abdul Haleem al-Ruhaimi, of the prime minister's national reconciliation office, said tribal divisions had discouraged Abadi from arming Sunnis in Anbar.
In the past, weapons intended for tribes fell into Islamic State fighters' hands.
"The speed with which police and army forces retreated from Ramadi gave a reasonable justification for government to urgently resort to the Hashid to restore balance. I don't see an issue as long as Hashid forces will be reporting to the commander in chief of the armed forces," said Ruhaimi.
Lingering caution over arming the Sunni tribes will give the Shi'ite militias more leverage and importance, especially if Islamic State has designs on other parts of Iraq.
Hassan Hassan, author of a book on the Islamic State group, said the Ramadi advance would discourage Sunnis who once mustered the courage to fight Islamic State militants from taking up arms.
"It's a game changer, it's basically like the last straw for any hope that you can actually get the Sunnis together to fight against ISIS," Hassan said.
Some Sunni tribal leaders were sympathetic with Abadi, saying his Shi'ite political rivals had capitalized on the panic over Ramadi to gain an upper hand.
"If it were in Abadi's hands, he would arm the (Sunni) tribes, but the (Shi'ite) parties are preventing him from doing so," said Sheikh Ziyad Munajid Suleiman from Ramadi. "He is a man who wants a solution, but he is under political pressure."