WASHINGTON • A Pentagon-led plan to defeat ISIS, due in draft form by Monday, will look beyond Iraq and Syria to include the threat from militants around the world fuelling the conflict, America's top general has said.

The remarks by Marine General Joseph Dunford, chairman of the Joint Chiefs of Staff, suggest the preliminary plan will be far broader in scope than initially thought and might omit more tactical details such as specific troop requests.

"This is not about Syria and Iraq. It's about trans-regional threat," Gen Dunford told a think-tank event in Washington, citing other militant groups like Al-Qaeda. "So, when we go to the President with options, it will be in the context of the trans-regional threat."

He noted US military estimates the Islamic State in Iraq and Syria had drawn 45,000 foreign fighters from more than 100 nations.

"Our plan, to be successful, needs to, No. 1, cut the connective tissue between regional groups that now form a trans-regional threat," the general said.

The US military-led review includes input from Secretary of State Rex Tillerson, as well as from the Treasury Department and the intelligence community.

Gen Dunford said it would also address ISIS' resources and a narrative that allowed it to declare a self-styled caliphate.

The review of strategy comes at a decisive moment in the US-led coalition effort against ISIS in Syria and Iraq, and could lead to a relaxation of some of the former Obama administration's policy restrictions, like limits on troop numbers.

The Baghdad-based commander on the ground, Army Lieutenant- General Stephen Townsend, has said he believes US-backed forces will recapture both of ISIS' major strongholds - the cities of Mosul in Iraq and Raqqa in Syria - within the next six months.

Iraqi forces expect a fierce battle against ISIS to retake Mosul.

In Syria, the United States must soon decide whether to arm Syrian fighters from the Kurdish People's Protection Units, despite objections from Nato ally Turkey, which brands them terrorists.

General Joseph Votel, head of the US military's Central Command, which oversees American forces in the Middle East, has told reporters travelling with him in the region that the US could ultimately need more of its forces in Syria to accelerate the campaign.

Meanwhile, on the ground in Syria, Turkish-backed rebels seized the town of al-Bab from the militants on Thursday, ending a grinding offensive to push the extremist group from one of its final strongholds.

Victory in ISIS' final stronghold along the Turkish border would deepen Ankara's influence in an area of Syria where it has effectively created a buffer zone. It would also allow Turkish-backed forces to press on towards Raqqa, the de facto capital of ISIS in Syria.

Also on Thursday, government forces in Iraq seized most of Mosul's airport, an important milestone in the broader offensive to retake the western half of the country's second largest city from ISIS militants.

REUTERS, NYTIMES, AGENCE FRANCE-PRESSE