Robert Ford was always one of the Syrian rebels’ loudest cheerleaders in Washington, agitating from within a reluctant administration to arm vetted moderates to fight Bashar Assad’s brutal regime.

In recent weeks, however, Ford, the former U.S. ambassador to Syria who made news when he left government service a year ago with an angry critique of Obama administration policy, has dropped his call to provide weapons to the rebels. Instead, he’s become increasingly critical of them as disjointed and untrustworthy because they collaborate with jihadists.

The about-face, which is drawing murmurs among foreign policy analysts and Syrian opposition figures in Washington, is another sign that the so-called moderate rebel option is gone and the choices in Syria have narrowed to regime vs. extremists in a war that’s killed more than 200,000 people and displaced millions.

On the heels of meetings with rebel leaders in Turkey, Ford explained in an interview this week why his position has evolved: Without a strong central command or even agreement among regional players that al Qaida’s Nusra Front is an enemy, he said, the moderates stand little chance of becoming a viable force, whether against Assad or the extremists. He estimated that the remnants of the moderate rebels now number fewer than 20,000. They’re unable to attack and at this point are “very much fighting defensive battles.”

In short: It makes no sense to keep sending help to a losing side.

“We have to deal with reality as it is,” said Ford, who’s now with the Middle East Institute in Washington. “The people we have backed have not been strong enough to hold their ground against the Nusra Front.”

Ford today sounds like a different person from the optimist who only six months ago wrote an essay in Foreign Policy that began: “Don’t believe everything you read in the media: The moderate rebels of Syria are not finished. They have gained ground in different parts of the country and have broken publicly with both the al Qaida affiliate operating there and the jihadists of the Islamic State.”

Now, however, on panels and in speeches, Ford has accused the rebels of collaborating with the Nusra Front, the al Qaida affiliate in Syria that the U.S. declared a terrorist organization more than two years ago. He says opposition infighting has worsened and he laments the fact that extremist groups now rule in most territories outside the Syrian regime’s control.

Ford said part of the problem was that too many rebels – and their patrons in Turkey and Qatar – insisted that Nusra was a homegrown, anti-Assad force when in fact it was an al Qaida affiliate whose ideology was virtually indistinguishable from the Islamic State’s. The Obama administration already has suffered a string of embarrassments involving supplies it’s donated to the rebels ending up in the hands of U.S.-designated terrorist groups.

“Nusra Front is just as dangerous, and yet they keep pretending they’re nice guys, they’re Syrians,” Ford said. “The second problem is, some of our stuff has leaked to them.”

As his calls to arm the rebels have become more muted, Ford has grown more vocal about the relationship between the rebels and Nusra, something U.S. officials have preferred to ignore, at least in public.

At a seminar last month where the audience included prominent Syrian dissidents he’d worked with for years, Ford began with a disclaimer that what he was about to say was “not going to be popular” among the opposition crowd.

He then launched into an indictment of the moderate rebels, pulling no punches as he told them they could forget about outside help as long as they kept collaborating with Nusra. He suggested that supportive U.S. officials had grown tired of covering for them before an administration and an American public that are skeptical of deeper U.S. involvement in Syria.

“For a long time, we have looked the other way while the Nusra Front and armed groups on the ground, some of whom are getting help from us, have coordinated in military operations against the regime,” Ford said. “I think the days of us looking the other way are finished.”

Most audience members were familiar with Ford’s record, and they were visibly surprised at the tongue lashing; they knew him as a relentless defender of the rebels, someone who’d ended a long diplomatic career a year ago this month with scathing words about the Obama administration’s refusal to arm them. Ford is often described as the first senior official to come out so vocally against U.S. policy toward Syria; the White House is still furious with his decision to go off-message.

Ford hasn’t softened his stance against the U.S. role in the Syrian catastrophe – he still describes American policy as “a huge failure” and “singularly unsuccessful” – but now he doesn’t spare the rebels their share of the blame. He has little patience for the argument that they were forced to work with Nusra and other unpalatable partners because of broken Western promises of assistance. There needs to be agreement, he said, that an al Qaida affiliate is off-limits as a partner.

“It becomes impossible to field an effective opposition when no one even agrees who or what is the enemy,” he said.

Ford said the latest U.S. approach of ditching the old rebel model to build a new, handpicked paramilitary to focus on the Islamic State was doomed; Syrian rebels are more concerned with bringing down Assad than with fighting extremists for the West, and there are far too few fighters to take the project seriously.

“The size of the assistance is still too small,” he said. “What are they going to do with 5,000 guys? Or even 10,000 in a year? What’s that going to do?”

The Assad regime is eager to present itself as an alternative, but Ford said the Syrian military had been severely weakened and that it was doubtful the regime could pull off a successful campaign against the extremists. Then there’s the political and moral fallout that would come from a U.S. détente with a man American officials have described since 2011 as a butcher who’s lost the legitimacy to rule.

Ford said the time had come for U.S. officials and their allies to have a serious talk about “boots on the ground,” though he was quick to add that the fighters didn’t need to be American. He said a professional ground force was the only way to wrest Syria from the jihadists.

And any parallel effort to build up a local rebel movement would have to be streamlined through a central, Syrian chain of command, he said. International partners, Ford said, have to ditch the current “nonsensical” framework in which regional powerhouses each fund client groups in an uncoordinated tangle that he said would be comical if the results weren’t so tragic.

And if those steps can’t be achieved, said the man known for advocating greater U.S. involvement, “then we have to just walk away and say there’s nothing we can do about Syria.”