Militants in Iraq have seized a broad swathe of territory in the northern and western regions of the country in recent weeks in their quest to topple the government of Prime Minister Nuri al-Maliki and to set up an Islamic caliphate.
Here's what you should know about the situation in Iraq:
Who are the militants?
The militants are from the Sunni Islamic State of Iraq and Syria (ISIS), also known as Islamic State of Iraq and the Levant (ISIL). The group grew out of an Al-Qaeda-linked organisation in Iraq and is led by Abu Bakr al-Baghdadi, an obscure figure regarded as a battlefield commander and tactician.
ISIS has 3,000 to 5,000 fighters including Europeans, Americans, Chechens, Turks and nationals from Arab countries, some attracted by the conflict in Syria.
The group follows an extreme interpretation of Islam which is anti-Western, promotes sectarian violence and targets those who do not agree with its interpretations as infidels and apostates.
What do they want?
The group aspires to overthrow both the Iraqi government and the Syrian regime of President Bashar al-Assad. It aims to establish an Islamic caliphate or state spanning Iraq, Syria and other parts of the Levant. The group already controls a large swathe of territory in eastern Syria and has begun imposing syariah law in some Syrian towns, forcing women to wear the full veil, or niqab, in public and banning music.
What have they seized?
Iraq has asked the United States to launch air strikes to stop the militant offensive, amid warnings that the country may break up. Experts say US President Barack Obama is mulling a sheaf of rather problematic options:
Troops on the ground:
The message from the White House is "no chance". Mr Obama, who brought troops home from Iraq, is not about to send them back.
Withdrawing from quagmires in the Middle East is so central to the DNA of the administration that to reverse course would repudiate the last five-and-a-half years. "The President was very clear that we will not be sending US troops back into combat in Iraq," said National Security Council spokesman Caitlin Hayden.
Mr Obama is on solid political ground. There is no public appetite to rewage a war in which nearly 4,500 Americans died.
Mr Obama has asked his national security team to prepare a range of other options that could help support Iraqi security forces.
A fallback option is US strikes, either from manned aircraft or unmanned drones. Such a tactic could still pack an explosive punch against the ISIS fighters, but avoid the kind of risk to US personnel.
With little in the way of hostile ground fire or anti-aircraft fire expected over Iraq, F-18 fighter jets could fly from a US aircraft carrier, the George H.W. Bush, deployed to the Gulf.
Although no major ground force would be required, air strikes could require a small number of American forward air controllers on the ground to direct bombing runs and prevent civilian casualties. The White House has 100 troops - reportedly special operations forces - at the ready just outside Iraq, which could be sent in.
Unless ISIS militants are moving in convoys visible on a desert highway to Baghdad, analysts say air strikes would require careful targeting as the extremists operate in populated areas.
But air controllers would represent a coveted target to militants, who would relish the chance to capture and kill an American.
Advocates of US intervention say American air power could hamper and disrupt ISIL forces, who would have to avoid gathering in large groups and operate in a more stealthy manner. And bombing raids could be crucial if ISIS fighters threatened Baghdad.
But the possibility of civilian casualties is not the only downside.
Even if initial raids worked, Washington would face the risk of an open-ended campaign and would have to decide when to call off the bombing.
Throughout his presidency, Mr Obama has favoured arms length warfare using unmanned aircraft to target Al-Qaeda and affiliated extremists. Such aircraft can hover for hours over a target, collecting intelligence, and then strike quickly and lethally if targets suddenly emerge.
Drones could also furnish intelligence and other battlefield information to Iraq forces engaging ISIS fighters.
But Washington would also have to acquire permission from Sunni Arab states where Predator and Reaper drones could be based, including Qatar, Kuwait and the United Arab Emirates for missions over Iraq.
Those countries distrust the Shi'ite-led government in Baghdad and may refuse to give a green light.
The Political Track:
Two and a half years after the last US troops left Iraq, the White House is expressing increasing frustration that Iraqi Prime Minister Nuri al-Maliki ignored calls to repay US sacrifices in Iraq by cementing democracy with a multi-ethnic, pluralistic state in which minorities feel they have an investment.
Mr Obama warns that equipment and training being contemplated for Iraqi forces would come with a condition - that Mr Maliki promote the kind of sectarian engagement that has so far been lacking. "In the absence of this type of political effort, short-term military action - including any assistance we might provide - won't succeed," Mr Obama warned.
But experts say if Mr Maliki had refused to embrace reconciliation with Sunnis in a time of relative calm, he is unlikely to do so now with his country splintering.
SOURCE: Reuters, AFP