Iraqi government forces backed by the US-led coalition are "on the cusp" of taking Islamic State's (IS) last major stronghold in the country, Defence Secretary Sir Michael Fallon has said.
Sir Michael, who has returned from a three-day visit to Iraq where he met senior government figures, said the operation to take the city of Mosul would begin "in the next few weeks".
Two years after the RAF began military operations against IS – also referred to as Daesh – he said UK warplanes were stepping up attacks on the militants' positions ahead of the offensive, striking more than 100 targets in and around the city.
"The RAF is now operating at the highest tempo in a single theatre for over 25 years," he told reporters at a briefing in London
"There is no doubt that Daesh is facing defeat. We are on the cusp of liberating the last major city in Iraq – Mosul.
"Having spoken to the commanders of the troops involved, their self-belief and determination is very clear.
"Though Mosul is a large and complex city, it will fall and will fall soon. I expect the operation for its encirclement to begin in the next few weeks."
Sir Michael, who reviewed the attack plan with commanders, said that Iraqi forces were moving into their tactical assembly ready for the assault.
Lieutenant General Mark Carleton-Smith, the deputy chief of the defence staff (operations), said coalition air strikes were keeping up the pressure on IS, destroying "close to a billion dollars" in IS's illegally held "cash stockpile".
"We are disrupting Daesh command and control with targeted strikes that are restricting their freedom of movement and their logistic resupply," he said.
Sir Michael acknowledged that the fall of Mosul would not mean the end of IS in Iraq, but said that it should be possible to drive them out of the country within the coming months.
"There remain pockets of Daesh resistance. However, we estimated at the beginning a three-year campaign. Two years on we have made significant progress. Daesh is a failing organisation," he said.
"We ought to be able to get Daesh out of Iraq over the next few months – the remaining months of this year and next year."
Coalition defence ministers will meet next month to discuss how to deal with the estimated 8,000 foreign nationals fighting with IS – including around 400 UK nationals – some of whom are expected to try to return to Europe.
"The partners in the coalition are very clear that their nationals who have gone off to fight and may have been involved in barbaric crimes should not be allowed to slip through the net without facing justice," he said.
Sir Michael acknowledged that the struggle against IS in Syria was "more complicated" but insisted that "significant progress" had been made.
He accepted however that the "Syrian democratic forces", which the coalition hopes will provide the ground force to take the IS stronghold of Raqqa, would need strengthening before they were ready to take on the militants.
The Defence Secretary also bitterly condemned the Russians whose warplanes he said "almost certainly" carried out the air strike on a UN aid convoy which effectively spelt the end of the brief ceasefire in Syria
"Instead of inventing more and more unbelievable excuses it is time Russia came clean," he said.
"If it was a mistake Russia should apologise. If it was deliberate then the Russian commanders should be turned in for prosecution."