LONDON (Reuters) – U.S. estimates of the number of Islamic State fighters in Iraq and Syria have been reduced while cuts in their pay are evidence they are on the defensive, a spokesman for the U.S.-led coalition fighting the group said on Monday.

But the task of defeating Islamic State is complicated by Russian air strikes in Syria which are 90 percent targeted at opposition fighters and not at the jihadist group, U.S. Army Colonel Steve Warren said.

Warren said increases in forced conscription, the recruitment of child soldiers and the use of elite fighters in common units were all evidence that Islamic State was seeing a slowing in the influx of foreign fighters.

“We believe that Daesh is now beginning to lose. We see them in a defensive crouch,” Warren told reporters in London, using an Arabic acronym for Islamic State.

U.S. intelligence estimates of the number of Islamic State fighters, which for the first 17 months of coalition operations ranged from 19,000 to 31,000, had been revised to 20,000 to 25,000 – a level he said the group would struggle to maintain.

“They have been able to replenish their forces at roughly the same rate as we’ve been able to kill their forces. That’s hard to sustain,” he said.

Warren said that until recently the average local Islamic State fighter was paid about $400 a month, while foreign fighters, who tended to be “better” because they were more committed and fanatical, were on $600 to $800 a month.

However, recent announcements by the group and other evidence suggested that common fighters pay had been cut by half, while it had also reduced pay for the foreign recruits, though perhaps not by such a large proportion, he said.