"There are places where ISIS is more powerful today than they were three or four years ago," Pompeo said on CBS's "This Morning" show.

"But the caliphate is gone in their capacity to conduct external attacks, it's been made much more difficult," he said.

"We've taken down significant risk. Not all of it, but a significant amount. We're very pleased with the work that we've done."

US President Donald Trump declared early this year that US-led forces in Syria and Iraq had achieved "100 percent victory" over the Islamic extremist group after a campaign to eliminate their redoubt in the Euphrates river valley in Syria.

But many fighters are believed to have melded into the population, and the group maintains small strong holds in remote locations in Iraq.

A report by the Pentagon's Inspector General earlier this month said IS is transitioning "from a territory-holding force to an insurgency in Syria," and has firmed up its insurgent capabilities in Iraq.

The US drawdown or reassignment of some security forces in the region has left some room for the group to rebuild, the report said.

The Islamic State has "established 'resurgent cells' in Syria and sought to expand its command and control nodes in Iraq," it said.

IS has also become a potent threat in Afghanistan, where it acts independent of the Taliban, which is currently negotiating a peace deal with the United States.

On Saturday the IS took credit for a suicide bombing of a wedding in Kabul that killed 63.

pmh/ch

CBS CORPORATION