BAGHDAD/ERBIL, Iraq (Reuters) - An Iraqi Shi’ite militia leader accused government forces of “betrayal” as a split emerged between the Iranian-backed paramilitaries and the army over tactics for fighting Islamic State.

The head of the largest militia, Hadi al-Amiri, criticized the army for moving an armored brigade to the Makhmour area near Mosul - Islamic State’s capital in northern Iraq - while the battle to dislodge the militants from Falluja, their stronghold near Baghdad, is still underway.

“Unfortunately there is an absence of precise planning for the military operations,” said Amiri, who leads the Badr Organisation. “I believe that sending a large number of armored vehicles and assets to Makhmour, under the pretext of the Mosul battle, is a betrayal of the battle for Falluja,” he told Al-Sumaria TV on Sunday.

Badr Organisation is the largest component of the Popular Mobilisation, a militia grouping which has been fighting alongside the Iraqi army at Falluja, with government units also receiving air support from the U.S.-led coalition.

Amiri also accused the Iraqi authorities of deciding to move the forces to Makhmour, which lies around 60 km (40 miles) south of Mosul, under pressure from the United States.

An army spokesman denied that the build up would affect the battle for Falluja, about 350 km south of Mosul, which the militias and Iraqi government forces are trying to regain after two years of Islamic State control.

The row reflects the diverging priorities of Prime Minister Haider al-Abadi - a Shi’ite who was elected in 2014 on a promise to mend rifts with the Sunni Muslim minority - and the Shi’ite militias backed by Iran.

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Falluja, which lies 50 km (30 miles) west of Baghdad, is a historic bastion of the Sunni insurgency against the U.S. occupation and then against the Shi’ite-led authorities that took over after the overthrow of Saddam Hussein, a Sunni, in 2003

Sunni politicians fear the participation of the Shi’ite militias in the assault could further inflame sectarian tensions.

HISTORIC BASTION

Amiri is the second militia official to voice dismay over the Falluja assault. On Friday, a spokesman for Asaib Ahl al-Haq, Jawad al-Talabawi, said the operations had come to a near standstill and asked Abadi to order the resumption of attacks.

Abadi said on June 1 that the army had slowed its offensive over fears for the safety of tens of thousands of civilians trapped in the city with limited access to water, food and healthcare.

Iraqi army officers confirmed that an armored brigade had arrived on Sunday night in Makhmour. This was part of preparations for an offensive to take an airfield that they plan to use in a future offensive on the city.

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Bridges and boats have also been brought to facilitate the crossing of the Tigris river from Makhmour to Qayyara, where the airfield lies, they said, giving no indication of when the battle would start.

Iraqi armed forces spokesman Brigadier General Yahya Rasool played down the effect of any mobilization to capture Mosul. “I don’t believe it would impact the ongoing battle of Falluja,” he told Reuters. “The forces allocated to Falluja are achieving victories and we have started moving toward the city center.”

Falluja was the first city captured by Islamic State in Iraq, in January 2014, six months before the group declared its caliphate over areas of Iraq and Syria. Abadi has expressed hope that 2016 will be the year of “final victory” over Islamic State, with the capture of Mosul.

Abadi ordered the offensive on Falluja after a series of bombings claimed by Islamic State hit Shi’ite districts of Baghdad, causing the worst death toll this year.

His initial decision seems to have gone against the plans of his U.S. allies, who would prefer the government concentrate on Mosul rather than risk getting bogged down in a protracted battle in a potentially hostile mainly Sunni area.

The government has already recaptured two cities from Islamic State - Saddam’s home town of Tikrit, and Ramadi, the capital of Iraq’s vast western province of Anbar.