US President Barack Obama on Thursday said he is prepared to send up to 300 military advisors to Iraq to help the official armed forces fend off the militant Islamist threat.
But he will only deploy ''precise military actions'' once intelligence on the ground improves and if the situation demands it. The Iraqi government has officially requested US air strikes against the Islamists.
A few teams of about a dozen advisors each are to arrive ''very soon'' from their bases in the region, a senior administration official said.
They are to focus first on helping Iraqi troops secure Baghdad, starting with the perimeter around Baghdad ''and making sure that that's not overrun'', Obama said.
A second joint operation centre is to be set up in northern Iraq. The advisors will deploy to Iraqi military headquarters and possibly brigades, a senior administration official said on condition of anonymity.
They will ''share intelligence and coordinate planning to confront the terrorist threat of ISIL'', Obama said.
Obama insisted that the presence of advisors would not signal a return to combat in Iraq, and his administration was careful to refer to the military personnel as 'advisors', not troops.
''We do not have the ability to simply solve this problem by sending in tens of thousands of troops and committing the kinds of blood and treasure that has already been expended in Iraq,'' he said.
The US will not send in soldiers to actively call in airstrikes, officials said.
House Democratic leader Nancy Pelosi raised concerns about even a small military mission to Iraq, warning that numbers have ''a tendency to grow''. Republican House Speaker John Boehner charged that ''the wheels were coming off'' of Obama's anti-terrorism efforts.
There was no reference to the unprovoked and one-sided war on Saddam Husain's Iraq spearheaded by previous US President George W Bush, which has led to the present mess in the country.
Obama warned that the growing prospect of civil war in Iraq poses the danger of a humanitarian crisis, destabilisation ''throughout the region'' and disruption of important ''energy and global energy markets'' that the US is committed to protecting.
The prospect of the jihadist Islamic State in Iraq and the Levant (ISIL) and other extremist groups gaining a base of operations across Iraq and Syria poses an additional threat to US national security, he said.
The Iraqi government insisted it was in full control of the country's largest oil refinery, after repulsing an offensive by Sunni-led insurgents.
''The security forces have tightened control of the Biji refinery and the surrounding area, keeping terrorists at bay,'' Iraq's oil ministry said in a statement. Army spokesman Gen Qassem Ataa backed up the statement.
The facility, some 200 km north of the capital Baghdad, accounts for almost a third of Iraq's refining capacity.
But Dubai-based al-Arabiya television reported that ISIL fighters were still present inside the facility, and a senior US administration official also indicated that a ''major battle'' was still going on there.
Security officials on Thursday reported clashes in the area of Baquba, 60 km north-east of Baghdad, between the Iraqi army and Sunni insurgents, including ISIL militants.
An air raid on an ISIL ''hide-out'' north of Baquba killed 15 members of the militant group, the news service of Alsumaria television reported online.
Obama noted the ''urgent need for an inclusive political process,'' but did not call for the pro-Shiite Prime Minister Nuri al-Maliki to step down as Parliament works to form a new Government.
US officials blame al-Maliki for failing to govern fairly in the interests of minority Sunni and Kurds and various tribes, thus fueling support for ISIL.