Britain's special forces will be "integral" to the offensive on the Islamic State (Isis) as the battle to liberate Iraq's second city from the clutches of the terror group looms.

Isis captured Mosul two years ago and the SAS is coordinating air strikes in and around the city with Kurdish fighters, according to the Times. The newspaper also quoted an unnamed Iraqi intelligence source as saying the elite forces are "more effective than any other advisers", including from the US.

Turkish President Recep Tayyip Erdogan said the assault on Mosul will begin on 19 October. British military personnel are also reportedly playing a key role in the information war, which is being place out on the airwaves and the internet.

Isis militants are being encouraged to put their weapons aside and residents are being prepared for the offensive with pro-government messages, the Times reported. The US has sent in Apache helicopters to aid the liberation effort.

"You need to condition the minds of the population," a British ex-senior officer was quoted as saying. "Owning the narrative is fundamentally important to success. Otherwise the people you are trying to liberate will respond badly."

Despite Isis' huge previous gains, territory controlled by the jihadists dwindled by 16% in the first nine months of 2016, according to IHS Conflict Monitor. General Gary Volesky, the head of US ground forces in Iraq, described Mosul as the "crown jewel right now."

Isis lost control of Manbij in Syria in August and rebels are now closing in on Dabiq, backed by Turkish tanks. The offensive in Mosul will involve multiple phases and will be led by the Iraqi army, Kurdish peshmerga forces, Sunni and Shia fighters and the US.

According to reports, the US is working to quell internal disputes between allies in the coalition. Part of the argument is over how the greater Mosul region of Nineveh will be governed post-liberation.