WASHINGTON - The United States is facing the limits of air power in the Syria border town of Kobane, where Islamic State jihadists are steadily closing in on Kurdish fighters despite a series of US bombing raids.
Fighter jets and drones from the world's most powerful air force have carried out at least eight attacks over the past week against the IS group near Kobane, but the air raids have failed so far to turn the tide in the battle for the strategic town near the Turkish border.
For some analysts and former US officials, the town's plight illustrates how bombing from the air has serious limitations without troops to guide the strikes to a target or a well-organised ally who can take advantage of the air raid.
The Kurdish defenders are far from a coherent army and are badly outgunned, said Seth Jones, a former adviser to US special operations forces.
"At this point, it looks like Kurdish fighters face a well-organised and well-funded ISIS (IS group) force," he said.
"This is a notable concern across Syria, where US airpower is not being coordinated well with ground forces - in part since there are a plethora of rebel groups in Syria," Jones said.
The number of US strikes near Kobane has been limited, and on a smaller-scale compared to some other locations, which some experts say reflects a murky intelligence picture.
Without forward air controllers in Kobane, fighter pilots likely find it difficult to distinguish friend from foe, particularly as the IS militants seek to move among civilians to conceal their location, said Ben Connable, a retired Marine Corps intelligence officer.
"We probably don't have good enough intelligence to separate all the prospective targets from friendly fighters," Connable, now a senior anlayst at the RAND Corporation think tank, told AFP.
Even with the advanced cameras and sensors on US warplanes, clearly identifying an enemy target remains difficult, and even more challenging in poor weather, Connable said.
"It's hard to tell," he said. "You may think you have identified something in a video, but you may not have."
But Kurdish leaders and some critics in Washington have accused President Barack Obama of taking an overly cautious approach, arguing that US air strikes could stop IS extremists in their tracks if it the full potential of American air power was unleashed.
Retired US Air Force lieutenant general David Deptula said the air crews flying the combat missions are hampered by cumbersome procedures and restrictive approval rules for strikes that are undercutting the impact of the campaign.
"There is a sense and there is feedback that there are too many people trying to micro-manage the application of air power," said Deptula, who oversaw air campaigns in Iraq and Afghanistan.
In Kobane, "there needs to be 24/7 constant overwatch, and every time there are ISIL (IS) troops, vehicles, weapons that are observed - they need to be hit immediately," he said.
The elaborate approval process for strikes is a legacy of the war in Afghanistan, he said, where US forces took extra precautions after disastrous mistakes that left civilians killed.
But he said the war in Syria and Iraq is a much different situation, where the targets are troops in trucks moving down roads and clearly on the move.
Pentagon chief Chuck Hagel has denied that the air campaign is being micro-managed by the president or his aides, and that the head of US Central Command, General Lloyd Austin, has full authority to wage an unfettered air war.
A senior defence official rejected any suggestion that the air strikes were being held up by meddling from the White House or bureaucratic rules.
"The idea that the war is being conducted out of the White House is wrong. General Austin (at Central Command) has all the authorities he needs," said the official, who spoke on condition of anonymity.
The Pentagon suggested Friday that the air strikes in Syria were not about altering the outcome of battles there but disrupting the IS group's supply lines to help offensives carried out by Iraqi forces next door.
"I just want to make sure that I stress again that the focus in Syria has really been about the sanctuary and safe haven they enjoy," spokesman Rear Admiral John Kirby told a news conference.
"In Iraq, it's really been much more focused on supporting Iraqi Security Forces and Kurdish forces on the ground."