PARIS • The United States will convene in Brussels next month a meeting of defence chiefs from all 26 nations taking part in the US-led coalition against the Islamic State in Iraq and Syria (ISIS), Defence Secretary Ashton Carter said.

The meeting in three weeks' time will include Iraq, he added.

"Every nation must come prepared to discuss further contributions to the fight," he said in Paris on Wednesday after meeting his counterparts from France, Britain, Germany, Italy, Australia and the Netherlands on how to accelerate the anti-ISIS campaign.

The next phase of operations will target de facto ISIS capital Raqqa in Syria and Mosul in Iraq, Mr Carter said.

The coalition is gaining ground on ISIS, which British Defence Secretary Michael Fallon said has lost 25 per cent of the area it controls in Iraq and 10 per cent in Syria.

A new focus of the US-led effort is to destroy the group's cash hoard, much of it from illicit oil sales.

Colonel Steve Warren, a Baghdad-based spokesman for the coalition, said nine strikes in Iraq and Syria in recent months have led to the destruction of "tens of millions" of dollars of this money.

"Striking these cash collection points hurts this enemy," he told Pentagon reporters in a video call on Wednesday.

The US military has released videos of air strikes on what it says are cash-collection facilities. In a video of an attack on a building in Mosul earlier this month, vast plumes of what appear to be money can be seen fluttering into the sky following a huge blast. Another cash collection facility in Mosul was hit on Monday, Col Warren said.

Evidence shows this focus on ISIS cash, combined with the continued bombing of trucks that ferry illicit oil around Syria, is hurting the group's bottom line, he added.

AGENCE FRANCE-PRESSE