Iraq conflict: Obama to 'review options'

US President Barack Obama has said he will take several days to decide what action to take over Iraq, but that no US troops will be deployed there, the BBC reported.

Any US involvement "has to be joined by a serious and sincere effort by Iraq's leaders to set aside sectarian differences," he said.

In recent days Sunni insurgents have seized the cities of Mosul and Tikrit, and are moving closer to Baghdad.

Iraq's most senior Shia cleric has issued a call to arms to fellow Shias.

The message from Grand Ayatollah Ali al-Sistani, which was read out at Friday prayers in Karbala, said: "Citizens who are able to bear arms and fight terrorists, defending their country and their people and their holy places, should volunteer and join the security forces to achieve this holy purpose."

There are reports that thousands have already joined Shia militias, which could play a crucial role in the defence of Baghdad, says the BBC's Richard Galpin who is in the city.

The Sunni insurgents - from the Islamic State in Iraq and the Levant (ISIS) - regard Iraq's Shia majority as "infidels."

Mr Obama told reporters that ISIS represented a danger not just to Iraq and its people but that "it could pose a threat eventually to American interests as well."

He said Iraq needed additional support to "break the momentum of extremist groups and bolster the capabilities of Iraqi security forces."