WASHINGTON (Reuters) - When Barack Obama ran for president in 2008, he built his reputation as an anti-war candidate by disparaging U.S. involvement in Iraq, adamantly insisting: "It's time to end this war."
Now, with Iraq's U.S.-backed government under its most serious threat since President Obama pulled out the last U.S. troops in 2011, he is being forced to consider what had previously seemed unthinkable - resorting to military force there again.
His challenge is to use military power carefully to help besieged Iraqis face down an Islamist insurgency without getting the United States drawn into an intractable conflict that would test war-weary Americans' patience.
With that in mind, Obama issued a calibrated message on the White House South Lawn on Friday: he has a variety of options, but none involving U.S. combat forces on the ground, and he will take several days to consider them.
"I think we should look at the situation carefully," Obama said.
Obama's objective is to use the promise of U.S. military force, such as airstrikes, as an enticement to Baghdad to take urgent steps to be more inclusive and stop the country from breaking up into sectarian enclaves.
"You don't shy away from using force and when you do, you use it effectively with a plan, but you don't overreach and you don't use it as a first resort," was how one senior administration official described White House thinking.
The president's deliberate approach, however, may not tamp down the chorus of complaints from domestic critics over what they say is Obama's tentative approach to dealing with crises abroad.
"It's a luxury we don't have. Events are unfolding too rapidly," Republican Senator John McCain told Reuters.
Senior U.S. officials insist Obama will not be badgered into a hasty decision by congressional critics, like House Speaker John Boehner, who accused him of "taking a nap" while chaos rages in Iraq.
Some of those finding fault now are the same people who consistently accuse Obama of not doing enough in Syria, where Obama condemned the autocratic president, Bashar al-Assad, but backed away from an earlier threat of airstrikes.
Senior officials now see three challenges for Obama in Iraq.
The first is to take short-term action to stop the well-armed forces of the radical Islamic State of Iraq and the Levant (ISIL) from overrunning Iraq and securing a base from which to launch external attacks, including on American targets.
This fits the principle he laid out in a speech at West Point last month, that the United States will use military force unilaterally if necessary "when our people are threatened, when our livelihoods are at stake, when the security of our allies is in danger."
A medium-term goal is to ensure Iraq has a plan to break down its sectarian divisions and unite the country, riven by strife between Shi'ite and Sunni Muslim factions.
A longer-term goal is to persuade Iraq's allies to buy into a process to help hold the country together, and to persuade Congress to approve a $5 billion counter-terrorism fund to help Iraq and other countries deal with the extremist threat over the long haul.
Reporting by Steve Holland; editing by G Crosse and David Storey