In the last year the Islamic State has lost a swathe of territory in Syria and Iraq that it had captured in 2014 and infamously then declared its "caliphate".

Iraqi forces backed by airstrikes from the global coalition expelled the group from Mosul last summer, while Syrian Democratic Forces (SDF) took control of Raqqa in neighbouring Syria in October.

"Despite crushing the so-called caliphate and exposing Daesh (the Islamic State group) ideology for the lie it is, we mustn't let up in our pursuit of these apocalyptic terrorists," said Ryan Dillon, an American colonel and spokesman for the coalition, in London.

He pointed to four "high value" Islamic State leaders who had been "eliminated" recently as evidence that "we have and we will keep the pressure on."

However, in Iraq the coalition has already adjusted from supporting the country's security forces in major combat operations to "stability operations", according to Dillon.

"We will tailor our support based on Iraqi requirements, with a particular emphasis on holding and securing liberated areas," he said.

Meanwhile in Syria, it remains focused on removing the group from its remaining territory but is also now supporting the SDF "in pursuing and targeting foreign terrorist fighters attempting to escape through neighbouring countries," the colonel added.

That effort to prevent foreign fighters who travelled to the region from returning to the West to carry out attacks is now critical, Terry Wolff, Deputy Special Presidential Envoy for the coalition, told reporters.

"The foreign terrorist fighter flow is really of great concern," he said.

Wolff added the coalition was trying to build global mechanisms for constantly assessing and updating the situation with returning fighters.

"We have tried... to encourage nations, and now obligate nations, to share information, to share biometrics information on foreign terrorist fighters," he said, referencing UN Security Council resolutions on the issue.

Wolff added the plan had extended to trying to put in place "watchlists that get shared internationally."

"That is the future of the global fight," the envoy said.

"The future of the coalition is trying to share -- radically share -- information and intelligence in a way that makes sense."