Iraq's volunteer Popular Mobilisation units, which had played a leading role in the ongoing assault on Tikrit, are freezing their participation in offensive operations, commanders said today.
The organisation -- called Hashed Shaabi in Arabic -- had repeatedly voiced its opposition to the involvement of the United States, which launched its first air strikes on Tikrit Wednesday.
Several commanders from the Badr organisation, a militia whose leader Hadi al-Ameri is a senior figure in the Hashed Shaabi, said the group was pulling back but not out of the operation.
"We consider this a break until the coalition issue is resolved," one commander, who gave his name as Baqir, told AFP in Awja, just south of Tikrit.
The Hashed Shaabi account for the bulk of the various government and allied forces who have been trying, since March 2, to dislodge diehard Islamic State militants holed up in the centre of Tikrit.
Another Badr commander confirmed the pullback, which he said was a result of "international pressure".
Iran had so far been the prominent foreign partner in Baghdad's largest operation against jihadists who swept through Iraq's Sunni heartland nine months ago.
But the operation was stalling, and the Iraqi government eventually requested strikes by the US-led anti-IS coalition to break the deadlock.
The Pentagon conditioned its intervention on an enhanced role for regular government forces and said Thursday that paramilitary forces had already started pulling back.
The move angered some Shiite militias, which have done much of the heavy lifting in recent operations and now accuse Washington of "hijacking victory" by sending warplanes more than three weeks into the operation.
It was not immediately clear whether all of Iraq's myriad militias were on the same page, but Badr commanders said the largest were.
Grand Ayatollah Ali Sistani, the most revered Iraqi Shiite cleric, warned against disunity among the forces involved in the anti-IS fight.
"We must focus on unifying the vision and coordinating the positions of all Iraqi sides," said Sheikh Ahmed as-Safi, delivering Sistani's Friday sermon in the holy Shiite city of Karbala.
