The Obama administration has found itself in a foreign policy and national security pickle of rare complexity with the apparent entry of Syria into the Iraq conflict on the side of the US-backed government in Baghdad as well as active Iranian military support for Iraqi Prime Minister Nouri al-Maliki.
Washington already was toeing a delicate line with Shiite Iran, which the US deems the world's most active state sponsor of terrorism, over their common short-term interest in turning back the advance of militant Sunni rebels in Iraq.
Now, to its dismay, Syrian President Bashar Assad - regarded in Washington as a pariah who should be ousted - has joined the club with what US and Iraqi officials say are airstrikes against the Islamic State of Iraq and the Levant in western Iraq. ISIS had been fighting Assad in Syria before turning its major focus to seizing large swaths of northern Iraq.
Assad is being supported by Iran in his country's own civil war with opposition forces, and a decision for Syria to hit ISIS on Iraqi soil is perhaps not surprising. While Maliki may not like Syrian attacks on Iraqi territory, "if it distracts the Islamic State from its trek towards Baghdad for a while, then they will welcome it," said Robert Ford, former US ambassador to Syria.
But as Iraq's other immediate neighbors - Jordan, Kuwait, Saudi Arabia and Turkey - bolster their defenses, the new fighting threatens to unravel a byzantine balance of Mideast alliances and enmities that the United States long has sought to manage.
The US is deploying 300 special forces to train and advise the Iraqi army and is conducting surveillance flights. Iran is also flying surveillance drones over Iraq in aid of Maliki's government, and on Tuesday, Syrian planes killed 17 people in a strike in Iraq's mainly Sunni Anbar province, according to US and Iraqi officials.
American and Iranian officials have had some direct discussions on the matter, though the administration has ruled out the prospect of direct military cooperation or coordination with Iran.
However, amid widespread concern, notably among Sunni Arab states and Israel, about the convergence of US, Iranian and Syrian policies on ISIS, President Barack Obama's national security team has scrambled to produce a consistent and coherent message to the region.
Administration officials said intervention by Syria was not the way to stem the insurgents, who have taken control of several cities in northern and western Iraq.
"We've made it clear to everyone in the region that we don't need anything to take place that might exacerbate the sectarian divisions that are already at a heightened level of tension," Secretary of State John Kerry said at a meeting of NATO foreign ministers in Brussels. "It's already important that nothing take place that contributes to the extremism or could act as a flash point with respect to the sectarian divide."
At the White House, spokesman Josh Earnest went further.
"The solution to the threat confronting Iraq is not the intervention of the Assad regime," he told reporters. "In fact, it's the Assad regime and the terrible violence that they perpetrated against their own people that allowed ISIL to thrive in the first place. The solution to Iraq's security challenge does not involve militias or the murderous Assad regime, but the strengthening of the Iraqi security forces to combat threats."
Administration officials have said repeatedly that the only way to resolve the crisis is for Iraqi leaders to come together and form a truly inclusive and representative government in which all three of the country's main ethnic and religious groups - Sunni, Shiite and Kurd - have a voice.
Yet, it remains unclear if Maliki is willing to allow such an administration to be formed, and as long as the crisis continues, Gulf Arab countries with their long and deep distrust of Iran in particular are watching Iraq with increasingly dire concern.
Underscoring the urgency, Kerry, who traveled to Baghdad and the Kurdish city of Erbil this week, was to meet in Paris on Thursday with the foreign ministers of Saudi Arabia, the United Arab Emirates, Jordan and Israel, plus the prime minister of Lebanon, to try to ease their fears and discuss how to attempt to coordinate a response.
In another sign of how critical the situation has become, Kerry will then fly to Saudi Arabia on Friday to hold similar talks with King Abdullah.
Karim Sadjipour, an Iran expert with the Carnegie Endowment for International Peace, said the situation in Iraq, coupled with ongoing US-Iran nuclear negotiations, have produced a "bizarre dynamic" in which the United States and Saudi Arabia appear to be "allies but not friends" and the United States and Iran appear to be "friends but not allies."
The addition to the mix of Syria's Assad is likely to further muddy the waters.
Full coverage: Iraq on the brink