– President Obama talks every day about defeating the Islamic State in Iraq and the Levant, but advisers say one option never surfaces for serious consideration — bringing the U.S. military in more directly to save the fledgling Iraqi security forces from their failures.

Obama doubled down on his approach last week in a meeting with top generals, who stood with him at the Pentagon as he explained his conviction that a large-scale investment of U.S. troops in another fight in the Middle East is a bad idea. He insisted that his military leaders agreed.

"In every one of the conversations that we've had, the strong consensus is that, in order for us to succeed long term in this fight against ISIL, we have to develop local security forces that can sustain progress," Obama said.

His position has plenty of challenges, particularly for a president trying to implement a long-term strategy on a short-term clock.

The timeline for the improvements Obama hopes to see — an Iraqi military that can take and hold ground, a resolution to the civil war in Syria, stability in either country — is not in his favor; they will probably come long after he's left office, if at all. Leading Republican critics are losing patience. They argue that ISIL's gains in Iraq and Syria and its expanded presence in Libya and Egypt, plus its persuasive recruitment campaign, prove Obama's strategy isn't working.

And then there is what top Obama aides see as the biggest problem: Iraq's inability to address rampant sectarianism. The president's national security apparatus is deeply concerned that too few Sunni Muslims are in positions of power, and that the Iraqi government relies too heavily on Shiite Muslim militias and Iranian advisers to fight ISIL.

Yet advisers to the president say that Obama is growing more resolute in his belief that slowly building up Iraq's capacity to defend its own territory is the only realistic way forward.

Although the alternative — more direct U.S. military involvement — could work in the short run, as the president has acknowledged, he frequently expresses the belief that the situation would quickly fall apart again as soon as American forces leave. He is unwilling to occupy Iraq indefinitely and believes the public feels the same, a conclusion that goes back to his promise as a candidate that he'd be the president who ends wars, rather than starts them.

Getting at the root causes

"If we came in and did it for them, it's not going to get at the root causes that allowed ISIL to have such dramatic momentum last summer," said a senior administration official. "We could quell the uprising, but that will not suffice if there is, at its root, this political and social divisiveness within the country. "That's the critical piece of the president's approach."

Obama's view dates to the beginning of his administration. In his earliest White House statements about the war in Iraq, he emphasized the importance of the Iraqis taking responsibility for their security.

In 2011, as the last American convoys were preparing to leave Iraq, aides noticed that Obama was inverting President George W. Bush's pledge that, as the Iraqis stood up, the U.S. would stand down. Obama's evolving view was that it would take the U.S. relinquishing responsibility before the Iraqis would govern.

Over the next four years, each new failure of the Iraqi security forces was seen in the White House as grim confirmation of Obama's assumption.

"This was a belief that ran all the way back to his campaign in 2008," said Julianne Smith, a former adviser on the White House national security team. "The question for him all along was, 'Will it be sustainable?' "

That remains an open question. In Sunni-populated areas such Anbar Province, citizens distrust their army.

To help ease the sectarian divide, the White House set up a training base last month in Anbar for outreach into Sunni tribal areas with the goal of drawing them into the fold. The U.S. has seen positive results over the last few weeks, with 1,300 Sunni tribal fighters enrolled in the Shiite militias.

Still, other problems persist. So far, the U.S.-led military training program in Iraq has only turned out about 9,000 Iraqi soldiers, far short of the 24,000 that the Pentagon envisioned.

And Defense Secretary Ashton Carter told lawmakers last week that the U.S. has trained just 60 Syrian opposition fighters to fight ISIL in that country, far below its goal.

"After four years, Mr. Secretary, that is not a very impressive number," Republican Sen. John McCain of Arizona, the Armed Services Committee chairman, told Carter.

The Obama administration announced in May that it hoped to train more than 5,000 Syrians a year at camps in Jordan and Turkey to form a moderate opposition in Syria. The program has been beset by setbacks, including the difficulty of finding recruits free of ties to extremists who want to fight ISIL, rather than forces loyal to Syrian leader Bashar Assad.

Some Iraqi officials are worried about the U.S. strategy.

Obama recently agreed to send 450 additional U.S. military trainers and support personnel — on top of the 3,100 already in place — to help with the training mission. Yet many Iraqi officials, who wanted the U.S. to take on a more active role, were let down.

Mowaffak Rubaie, Iraq's former national security adviser and now a lawmaker, accused the White House of failing to articulate its strategy against ISIL and said it doesn't seem to be willing to commit to the fight.

Anticipating the next president

He has asked the Obama administration to send U.S. troops to the front lines to direct coalition airstrikes, especially in densely populated areas where it can be difficult to tell friend from foe. But that seems unlikely, so Rubaie is turning his attention to a new U.S. president in 2017.

"We hope the next U.S. administration will be more engaging and proactive," he said, describing a not-so-veiled frustration with Obama. "At least we will know what the U.S. strategy is."

White House officials have come to expect regular attacks on Obama's viewpoint, especially when ISIL takes more territory.

Republicans generally see those losses as proof that Obama's strategy is flawed. On the campaign trail, several GOP candidates blame Obama's failure to leave a residual force in Iraq. Notably, though, his critics, including McCain, have yet to offer an alternative long-term solution.

Speaking at the Pentagon last week, Obama made clear his growing comfort with the criticism.

"If we try to do everything ourselves all across the Middle East, all across North Africa, we'll be playing whack-a-mole," he said. "And there will be a whole lot of unintended consequences that ultimately make us less secure."