Two senior senators have reportedly urged the US Federal Government to expand military forces in the fight against Islamic State of Iraq and Syria (ISIS).

Senate Committee on Armed Services chair John McCain and member Lindsey Graham criticised US President Barack Obama’s incremental strategy to defeat the terrorist group through airstrikes and assisting local forces.

Graham was quoted by Reuters as saying: "The only way you can destroy the caliphate is with a ground component.

"The aerial campaign is not turning the tide of battle."

About 3,500 US troops are currently advising and assisting Iraqi forces against ISIS.

"The aerial campaign is not turning the tide of battle."

In addition to US soldiers, McCain has called for 100,000 foreign combatants, with most coming from Sunni countries such as Egypt, Turkey and Saudi Arabia.

Graham further added: "If you went up to 10,000, you’re not getting pushback from the Iraqis.

"The difference between 3,500 and 10,000 is meaningless politically inside the country (but) militarily significant."

Obama had recently retorted to critics of the strategy, saying: "We would see a repetition of what we’ve seen before, which is if you do not have local populations that are committed to inclusive governance, and who are pushing back against ideological extremes, that they (terrorists) resurface unless we’re prepared to have a permanent occupation of these countries.

"And let’s assume that we were to send 50,000 troops into Syria. What happens when there’s a terrorist attack generated from Yemen? Do we then send more troops into there? Or Libya perhaps? Or if there’s a terrorist network that’s operating anywhere else in North Africa or in Southeast Asia?

The White House has also announced plans to intensify the anti-ISIL campaign against terrorists in Iraq and Syria.

The newly adopted strategy is aimed at curbing the Islamic State’s financing, thereby interrupting its supply lines and external support.