U.S. President Barack Obama is constructing a strategy for an increasingly complex war he never wanted to enter. And allies in the region are skeptical.

Now that ISIS controls a third of the combined territory comprising Syria and Iraq, the U.S. is attempting to establish an international coalition to "degrade and destroy" the well-armed and well-funded Islamic State.

The administration has begun to outline a three-pronged strategy that could last more than three years — and into the next administration. It consists of continuing to bomb ISIS targets from the air in Iraq, intensely moving to equip and train the Iraqi military and Kurdish forces, and then moving to confront the group in Syria.

A successful U.S.-led campaign to eradicate ISIS requires direct military action on both sides of the Iraq-Syria border, several years, billions of dollars, and tens of thousands of troops, according to counterterrorism expert Brian Fishman. "And even then," Fishman said, "success hinges on dramatic political shifts in both Iraq and Syria that under the best of circumstances will require years."

But Obama needs partners in the region as the president says he will not recommit conventional American troops to either Iraq or Syria and already backed off military action against the Syrian regime of Bashar Assad amid nuclear negotiations with Iran.

The challenge, as described by the Associated Press, is "overcoming the reluctance of U.S. allies in the Middle East who are deeply frustrated with a White House that they believe has been naive and weak on Syria’s civil war."

The reluctance of crucial countries like Turkey and Saudi Arabia exposes a big flaw in Obama's plan: He can't "degrade and destroy" ISIS without going into Syria but the U.S. can't beat ISIS in Syria without a ground force. And the only viable group — the national opposition fighting the regime of Syrian president Bashar Assad — has repeatedly dismissed by the administration.

Activists in Kafranbel, Syria, present an illustration of U.S. President Barack Obama watering a black piranha plant that stands for ISIS. Kafranbel activists

"The U.S. and the West have avoided the Syrian conflict for two years, essentially permitting the conditions that spawned ISIS," said Clint Watts, counterterrorism expert at the Foreign Policy Institute.

The Obama administration's nominal partner on the ground in Syria is the Free Syrian Army, which Obama has repeatedly disregarded as "an opposition made up of former doctors, farmers, pharmacists, and so forth."

But tens of thousands of Syrian Army defectors also joined the revolution, and the FSA became part of a Western-backed project to build a cohesive, national, and democratic opposition that could fill the potential power vacuum following President Assad’s fall."

The rub is that Obama decided in 2013 that the U.S. wouldn't “get in the middle of somebody else's civil war," and the White House only allowed the CIA to "provide enough support to help ensure that politically moderate, U.S.-supported militias don’t lose but not enough for them to win."

The general military situation in Syria as of September 2014. @Arabthomness Consequently, the nationalist opposition has struggled.

"The leadership of the FSA is American," a veteran FSA officer who defected from the Syrian army two years ago and won respect for leading rebel forces in southern Syria told McClatchy recently. "The Americans are completely marginalizing the military staff."

Over time, the FSA has been worn down by war against both the Syrian army and ISIS, which the Assad regime fostered for its own survival.

ISIS and the regime are squeezing the nationalist opposition in Syria's largest city, Aleppo, the only city where the FSA has a significant presence.

Free Syrian Army spokesman Hussam al-Marie told The New York Times that the loss of Aleppo would be “unrecoverable” and “a blow to our shared goals of a moderate Syria.

To defeat ISIS, the U.S. commander in chief will have to eventually confront the Assad regime — a move that would strain tensions with an increasingly assertive Iran.

Handing Off Iraq To Iran

The ISIS crisis highlights that Iraq also deteriorated amid U.S. indifference in recent years and may fracture completely if the current trajectory continues.

"It's not my job to rate the Obama administration's actions in Iraq," Baghdad Bureau Chief of The New York Times Tim Arango said on Reddit on Monday. "But I will tell you that after 2011 the administration basically ignored the country. And when officials spoke about what was happening there they were often ignorant of the reality."

Ali Khedery, the longest continuously serving American official in Iraq (2003-09), told Reza Akhlaghi of the Foreign Policy Association that the Obama administration "betrayed the promises that the U.S. government had made to the Sunni tribal leaders," who had previously fought with American troops against ISIS-predecessor Al Qaeda in Iraq (AQI) during the Iraq War.

America's continued support of Iraqi Prime Minister Nouri Maliki in December 2010 and beyond made it so that "Iraq’s path toward civil war was really inevitable," Khedery said, as Maliki steered Baghdad "toward a very pro-Iranian and sectarian agenda, which inevitably disillusioned and disenfranchised Sunni Arabs for a second time."

Iranian Supreme Leader Ayatollah Ali Khamenei with Iraqi Prime Minister Nouri al-Maliki in Tehran on Oct. 18, 2010. REUTERS/Khamenei.ir

Throughout 2014, powerful Sunni tribes and ousted Saddam-era Baathists have coordinated with ISIS to capture much of central, western, and northern Iraq. On the other side are demoralized Iraqi troops and increasingly sectarian Iranian-trained militias, some of which had been fighting in Syria.

The U.S. didn't truly tune into the crisis until after a few hundred ISIS militants overran Iraq's second-largest city of Mosul on June 10.

"There was a concerted effort by the administration to not acknowledge the obvious until it became so apparent — with the fall of Mosul — that Iraq was collapsing," The New York Times' Arango said on Reddit.

"Obama was hugely (and understandably) reluctant to authorize the use of force in Iraq — he considered ending the war there one of his chief accomplishments as president," geopolitical expert Ian Bremmer, the president of Eurasia Group, told Business Insider recently.

"But there wasn't much choice, as ISIS forces proved far more capable than U.S. intelligence had assessed, " he said.

Since Aug. 8, the U.S. has been bombing targets while Iraqi soldiers, Kurdish fighters, and Shia militiamen battle Sunnis on the front lines.

The fight on the ground is reportedly run by Qassem Suleimani, the head of the Qods Force, the foreign arm of Iran's Revolutionary Guards.

"While [the U.S. and Iran] say they are not coordinating, the U.S. has been bombing from above while Iranian-backed Shia militias, which a few years were killing American soldiers, have been doing the fighting on the ground, for the same cause," Arango said.

The ongoing American air war in Iraq occurs amid a territorial power struggle between Iran-backed Shia militias, ISIS, the Kurds, Sunni tribes, and Iraq's fledgling army.

A fighter from the Shi'ite Badr Brigade militia wears a religious flag on Friday as he guards a checkpoint that was recently taken from militants of the Islamic State outside the town of Amerli. REUTERS/Ahmed Jadallah

Endgame

And as the Middle East hurdles into a highly sectarian future, the U.S. faces the challenge of fighting ISIS in a way that doesn't alienate regional Sunnis while empowering sectarian policies of Iran and Assad.

"The key is to detach moderate Sunnis, the vast majority of Sunnis, from ISIS, by providing them with security and with a political alternative to rule by Iran and its proxies," Mike Doran, senior fellow at the Center for Middle East Policy, told Business Insider. "Iran and Syria have no assets that can counter the ISIS threat without making matters worse."

But Obama's Middle East strategy of backing away from the region while making a historical accommodation with Iran has made the challenge of defeating ISIS even more difficult.

"No wonder, then, that Obama’s policies are in a shambles," Doran wrote last month. "It is impossible to succeed in the Middle East without partners, and so long as he remains bent on empowering Iran and its proxies (who, for their part, continue to make no secret of their loathing for the United States), America’s traditional allies will withhold their own support for Washington’s initiatives."