Cairo (AFP) - Arab League chief Nabil al-Arabi on Sunday called for a military and political confrontation with Islamic State jihadists and other militants he said threatened the existence of Arab states.

"What is needed is a clear decision for a comprehensive confrontation, militarily and politically," Arabi said at a meeting of Arab foreign ministers, a day after he and US Secretary of State John Kerry discussed taking action against the jihadist group that controls swathes of Iraq and Syria.

The United States is looking for broad support for its campaign against the jihadist group, which its air force has already targeted in Iraq.

An Arab League diplomat told reporters that the ministers were considering adopting a resolution on combating IS and "coordinating with the United States to confront this terrorist organisation".

Iraq earlier welcomed US President Barack Obama's plan for an international coalition against jihadists as a "strong message of support," after repeatedly calling for aid against the militants.

Obama outlined the plan at a NATO summit Friday for a broad coalition to defeat IS, which led an offensive that overran parts of Iraq in June and also holds significant territory in neighbouring Syria.

IS, originally an Al-Qaeda affiliate in Iraq that expanded in the Syrian conflict, claims its chief Abu Bakr al-Baghdadi is the rightful leader, or Caliph, of all Muslims.

The group's astonishing rise in Syria and neighbouring Iraq caught the weak government in Baghdad, and much of the region, off guard.

Arabi said IS posed a threat to the existence of Iraq and other states in the region.

"What is happening in Iraq is that the terrorist organisation not only threatens a state's authority, but threatens its very existence and the existence of other states," he said.

The United States expanded on Sunday its month-long air campaign against the militants in Iraq's Sunni Arab heartland, hitting IS fighters west of the capital Baghdad as Iraq troops launched a ground assault.

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Aside from fighting in Iraq, Arab states are concerned that IS is coordinating with domestic extremists and that militants who travelled to fight with them may conduct attacks when they return home.

In Egypt, several militants who have carried out attacks on security forces since the army overthrew Islamist president Mohamed Morsi had travelled to fight in Syria.

The main Egyptian militant group, Ansar Beit al-Maqdis, has not publicly pledged its loyalty to IS but has refered to the jihadists as "brothers".