A centerpiece of the U.S. war plan against ISIS is in danger of collapsing. A key rebel commander and his men are ready to ready to pull out in frustration of the U.S. program to train a rebel army to beat back the terror group in Syria, The Daily Beast has learned.

The news comes as ISIS is marching on the suburbs of Aleppo, Syria’s second-largest city. Rebels fighting the jihadists there told The Daily Beast that the U.S.-led coalition isn’t even bothering to respond to their calls for airstrikes to stop the jihadist army.

Mustapha Sejari, one of the rebels who says he's approved for the U.S. training program, told The Daily Beast that he and his 1,000 men are on the verge of withdrawing their candidacies. The issue: the American government’s demand that the rebels can’t use any of their newfound battlefield prowess or U.S.-provided weaponry against the army of Bashar al-Assad or any of its manifold proxies and allies, which include Iranian-built militias such as Lebanese Hezbollah. They must only fight ISIS, Washington insists.

“We submitted the names of 1,000 fighters for the program, but then we got this request to promise not to use any of our training against Assad,” Sejari, a founding member of the Revolutionary Command Council, said. “It was a Department of Defense liaison officer who relayed this condition to us orally, saying we’d have to sign a form. He told us, ‘We got this money from Congress for a program to fight ISIS only.’ This reason was not convincing for me. So we said no.”

But the Pentagon says this story just isn't so.

"While we will not release the names and identities of any groups or trainees in the train and equip program, the T&E program trainers have never worked with Mustafa Seijari," Defense Department spokesman Col. Steven Warren emailed The Daily Beast, using an alternate spelling for the rebel commander.

Many Syrians rebels who have applied for the train-and-equip program are said to be confused about their status, not knowing whether they've made the cut or not. But applicants now say they won't join if they have to forswear war on the Assad regime.

And that's a serious issue. Rebel disaffection and possible withdrawal wouldn’t just mean the loss of a few fighters for the anti-ISIS army the U.S. is trying to assemble. It could mean a fracturing of the entire program—a cornerstone of the Obama administration’s plan to fight ISIS in Syria.

“The train-and-equip program will be structurally impaired for as long as those taking part in it are asked to target jihadists first and the regime second,” Charlie Winter, an ISIS specialist at the London-based Quilliam Foundation, told The Daily Beast. “It would be naïve to think otherwise: No opposition group will take kindly to being told that they can only be assisted if they focus their efforts on ‘terrorists’ and not the regime that got Syria to this position in the first place.”

Even worse, Sejari added, is that by openly aligning with the United States as a counterterrorism proxy, his troops will have a bull’s-eye painted on its back for all comers—al Qaeda, the regime, Iran and Hezbollah. That force, the al-Ezz Front, broke off from a Saudi-backed umbrella opposition group that was routed by Jabhat al-Nusra, the al Qaeda affiliate, in northern Syria in March.

“[My men] don’t want to be beholden to this policy because it can be used against them in Syria—that they’ve betrayed the revolution and now they’re just mercenaries for the coalition forces,” Sejari said.

Sejari has worked for years with the so-called “joint operations command” in Turkey, where the CIA and a host of Western and regional spy agencies have coordinated with vetted moderate rebels—sometimes arming them, although without the stifling proscription on whom they couldn’t fight. “In the past, we got some support through the [Western-backed] Friends of Syria group. Very small amounts. We were hoping there would be more support from the Americans,” Sefjari said.

“The American intelligence services have a fair idea who the good guys and bad guys are in Syria and they know which groups are fighting both extremism and dictatorship,” Sejari said. “If the Obama administration were sincere in putting an end to the suffering of the Syrian people, they could do that in three months.”

As approved by Congress, the Syrian train-and-equip program would be overseen not by intelligence officers but by the American military—definitely in Jordan and Turkey, and likely also in Saudi Arabia and in Qatar. But Ankara and Washington have never agreed on the remit of the mission, with Turkey insisting that these rebels be given air support given that they’ll be targets of the regime’s fighter jets and attack helicopters. Although U.S. Defense Secretary Ash Carter has floated the idea of American air support for the rebels publicly, the administration hasn’t committed to that and likely won’t. According to The Wall Street Journal, Obama worries that if any of his built-up Arab strike teams go after the regime in Syria, then Iran’s Revolutionary Guards Corps-Quds Force will instruct its Shia militias to turn their guns on U.S. personnel in Iraq.

The original goal was to graduate 5,000 battle-ready rebels per year, although the program has suffered numerous setbacks and delays since its inception. In early May, Carter told reporters at a Pentagon press conference that just 90 rebels were being put through the first round of training in Jordan. Colonel Patrick Ryder, a spokesman for CENTCOM, said 3,700 Syrians had volunteered in total, but of that number just 400 were approved with another 800 were being processed. This followed from an earlier announcement, in April, that Major General Michael Nagata, the man tapped by Obama to spearhead train-and-equip, was stepping down for unknown reasons (CENTCOM subsequently denied that Negata was quitting.). It doesn’t inspire confidence, Sejari said, that he didn’t know who was in charge of the program he wants nothing to do with anymore. “We don’t know what happened to General Nagata. No one tells us anything,” he added.

Sejari said that even if he were to sign up, he doesn’t think the result would greatly alter the balance of power in Syria or further stated U.S. objectives. “If anyone with any military knowledge examines this program, he will realize this program is not designed to make an impact or support the Syrian people. It will only contribute to dragging out this conflict much longer,” Sejari said. “We’ve been fighting for four years. Program, no program—we’ve been fighting for four years. If the Americans don’t change this precondition, we will carry on fighting.”

In another uninspiring development for the Levantine arm of the war, a major rebel commander has told The Daily Beast that no matter how hard he tries, he still cannot get the coalition’s attention for directing airstrikes against ISIS. And that’s allowing the jihadists to make major gains near the city of Aleppo, a stronghold of both moderate and Islamist rebels.

“We were hoping that we could work hand-in-hand with coalition forces to defeat ISIS and that the coalition would launch strikes against ISIS-held positions in northeast Aleppo. We called on them to do so,” Brigadier General Zaher al-Saket told The Daily Beast in a May 29 Skype interview.

Al-Saket defected from the Syrian Army in March 2013. He had been an officer in Assad’s chemical weapons division and today heads both the Aleppo Military Council and the Chemical Weapons Documentation Center, which compiles evidence of chlorine gas attacks perpetrated by his former comrades on Syrian civilians.

“For the past 24 hours, numerous towns in the northern Aleppo suburbs have been under constant bombardment by Daesh,” al-Shaket said, using the pejorative Arabic acronym for ISIS. “The jihadists captured Sawran, a key town, and is now advancing on two others including Marea, the nerve center for the rebel groups in Aleppo. The fall of Marea would severely weaken our capacity across the province. Hundreds of shells have rained on houses in Sawran and Marea. Ninety percent of the civilians in Marea had to flee to neighboring areas because their houses were destroyed. The terrorism carried out by ISIS is not very different from the terrorism being carried out by Assad.”

And in some ways, Assad’s Syria Arab Army (SAA) and ISIS are helping one another around Aleppo, where the regime is reported bombing rebel positions. “By attacking opposition positions around northern Aleppo, ISIS has granted the Assad regime a tactical opportunity, one that it has already begun exploiting,” Winter said. “This is not the first time the SAA and ISIS have benefited each other, and it will not be the last.”

For weeks, al-Saket has made numerous media appearances in Arabic-language outlets such as Al Jazeera and Orient TV calling for close coordination between his rebels and the coalition. He said he has precise coordinates for ISIS-controlled installations and materiel in towns such as Raei, Manbej, and al-Bab in the Aleppo suburbs. But so far, no one from U.S. Central Command—the arm of the American military responsible for the Middle East—has reached out to him.

ISIS launched their assault on northern Aleppo before the weekend, apparently after it caught wind of a the Syrian opposition’s plan to retake the rest of the province from the Assad regime, putting it in control of key supply corridors currently trafficked by ISIS.

The rebels’ idea is to replicate the success of Jaysh al-Fateh, a consortium of Islamist and jihadist rebel groups, largely led by al-Nusra, which has had stunning success in driving the regime out of Idlib province over the past month. Al-Saket said that while al-Nusra is not part of forces under his command, there was no denying that the al Qaeda franchise was also at war with ISIS in the province. “If ISIS is able to capture all the northern suburbs of Aleppo, that would mean they’d control the borders with Turkey. I don’t have to tell you what this means for the rebels.”

As al-Saket spoke to The Beast, he was interrupted by a fresh intelligence report from his field commanders saying that that white cars with blue covers were en route from Dabiq, an ISIS-controlled town in northern Aleppo, toward Hetemlat whence they’d no doubt proceed onto Marea. The cars were outfitted with explosives and driven by ISIS suicide bombers.

“The Syrian-American community asked the Obama administration for airstrikes on ISIS near Marea many months ago,” complained Mohammed Alaa Ghanem, the senior political adviser for the Syrian American Council, a Washington, D.C.-based opposition group in constant contact with the Aleppo Military Council. He said passed Sejari's concerns about the Pentagon's training program on to the State Department, the National Security Council, and offices of top U.S. lawmakers -- including Sens. John McCain, Bob Corker, Marco Rubio, and Harry Reid.

“We were rebuffed for the astounding reason that aiding the rebels in Aleppo would hurt Assad, which would anger the Iranians, who might then turn up the heat on U.S. troops in Iraq. The rebels are the only ones who can fight ISIS in northern Syria—Assad forces are losing ground rather quickly now—so I hope President Obama will reconsider his willingness to compromise the ISIS fight for the sake of an Iran deal.”

“ISIS is a metastasizing threat, not just for Syria but for the world,” al-Saket agreed, before hanging up to tend to the incoming car bombs.

UPDATE 3:13 PM: This story has been updated to include a denial from the Pentagon.