Republican presidential nominee Donald Trump is under fire for comments made on the progress of US-backed coalition Iraqi troops’ progress in liberating the city of Mosul from Isis.

“The attack on Mosul is turning out to be a total disaster. We gave them months of notice. US is looking so dumb. VOTE TRUMP and WIN AGAIN!,” a tweet sent last Friday read, which has been blasted by security experts as “unhelpful."

Despite criticism from several quarters over the weekend that he appeared to be rooting for US defeat in the complex operation to free Mosul, Mr Trump this week doubled down on his prediction that Operation Inherent Resolve will fail.

The US and its Iraqi partners should have planned a “sneak attack” on the Isis stronghold, he said - something experts say would be impossible given the large size of the city, the number of troops involved, and the flat plains surrounding Mosul for miles.

“You see what’s going on. You see how badly that fight is going,” Mr Trump said. “If you want to go into Mosul, you don’t tell people for four months. Now they are having a hard time and they are really dug in, and the people that we wanted, the leaders of Isis, are gone.”

Speaking to BBC Radio 4’s Today programme on Wednesday, Charlie Winter of the International Centre for the Study of Radicalisation at King’s College London said Mr Trump’s comments were actively damaging in the fight against extremism.

“Donald Trump is a fantastic recruitment sergeant for Isis,” he said.

The comments come on top of an earlier claim to be more knowledgeable about the extremist group than Obama’s military officials.

“I know more about Isis than the generals do, believe me,” he told NBC in September.

Mr Trump has changed his tune on how best to deal with Isis before he even announced his presidential candidacy last year, more than once claiming that he is keeping his “foolproof” plans to defeat the group “secret.”

Iraqi Christians celebrate liberation from Isis Show all 10 1 /10 Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis An Iraqi Christian prepares for the first Sunday Mass at the Church of the Immaculate Conception in Qaraqosh Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis Iraqi priests hold the first Sunday mass Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis Iraqi Christian soldiers attend the first Sunday mass at the Grand Immaculate Church since it was recaptured from Islamic State in Qaraqosh Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis An Iraqi Christian soldier holds his weapon during the first Sunday mass Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis An Iraqi Christian soldier lights a candle Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis Iraqi priests hold the first Sunday mass at the Grand Immaculate Church since it was recaptured from Islamic State Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis Iraqi priests hold the first Sunday mass Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis Iraqi Christian soldiers attend the first Sunday mass at the Grand Immaculate Church since it was recaptured from Islamic State in Qaraqosh, near Mosul in Iraq October 30, 2016. REUTERS/Ahmed Jadallah - RTX2R245 Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis An Iraqi Christian soldier attends the first Sunday mass at the Grand Immaculate Church since it was recaptured from Islamic State in Qaraqosh, near Mosul in Iraq October 30, 2016. REUTERS/Ahmed Jadallah - RTX2R256 Reuters Iraqi Christians celebrate liberation from Isis Iraqi Christians celebrate liberation from Isis Iraqi Christian soldiers attend the first Sunday mass at the Grand Immaculate Church since it was recaptured from Islamic State in Qaraqosh, near Mosul in Iraq October 30, 2016. REUTERS/Ahmed Jadallah - RTX2R269 Reuters

One thing he has repeatedly said is that he would “knock the hell out of Isis” - but US backed forces’ attempts to finally do that after Isis seized Mosul two years ago appear not to have impressed him.

A 30,000 coalition of Kurdish Peshmerga, Sunni tribal fighters, Shiite militias and Iraqi army troops have been making uneven but steady progress since the assault on Mosul began on October 14, moving the frontline forward village by village in an operation complicated by fierce Isis counterattacks on other cities, suicide bombers, and landmines littered around the countryside.

On Tuesday, units from Iraq’s elite Counter Terrorism Service reported that they had finally entered Mosul’s city limits from the east. The battle is expected to be slow and gruelling as coalition troops attempt to secure the city building by building from the estimated 4,000 fighters inside.

Isis releases video claiming everything is fine in Mosul

Presidential rival Hillary Clinton also called out Mr Trump at a rally in New Hampshire on Monday.

“This is a guy who says he knows more about Isis than the generals. I don’t think so,” she said.