President Donald Trump has made no secret of his desire to remove US troops from Syria. But his administration’s latest plan for how to do that is unlikely to materialize — and would be dangerous if it did.

Here’s the idea, as reported by the Wall Street Journal: Saudi Arabia, the United Arab Emirates, Qatar, and other Arab states like Egypt would band their troops together and form an “Arab force” to keep ISIS at bay in Syria.

That may sound good in theory, but there are several problems in practice. First, there’s little chance the majority of Arab countries in question would agree to such a plan. Saudi Arabia is in discussions with the US to send troops into Syria, according to Saudi Foreign Minister Adel al-Jubeir, but it’s unclear if other Arab states will follow suit.

Second, experts say their militaries would struggle in a campaign against ISIS. “No Arab state has the military or institutional capacity needed for this sort of task,” Faysal Itani, a Middle East security expert at the Atlantic Council think tank, tells me. “Arab armies are bad at counterinsurgency, and even worse at war,” he adds.

It’s unclear as of now if a remnant of US troops in Syria would remain to train and support the Arab forces. That seems unlikely, though, as Trump has indicated he wants to bring all of America’s 2,000 troops back home and let Middle Eastern counties take care of stabilizing Syria.

Finally, the Arab countries’ goals when it comes to intervening in Syria aren’t necessarily the same as the US’s. The Trump administration is exclusively focused on defeating ISIS and stabilizing the areas it once held to make sure the terrorist group doesn’t just come right back.

But James Jeffrey, a former top Middle East security official in the George W. Bush administration, explains that fighting ISIS is not the primary focus for the countries that would theoretically make up this new Arab force. “The Saudis and Emiratis want a policy focused on countering Iran and working against [Syrian President Bashar al-]Assad,” says Jeffrey.

It would also pit the military forces of two mortal enemies — Iran and Saudi Arabia — directly against each other in Syria, potentially provoking a dangerous and unnecessary escalation in the already horrifically bloody Syrian civil war.

“In sum,” says Jeffrey, the Trump administration’s plan for an Arab force is “not well thought out.”

Why an Arab force is unlikely

The politics surrounding the creation of an “Arab force” are so complicated that it’s surprising the Trump administration even considers it an option.

Take Saudi Arabia and the UAE. They’re in the midst of a US-backed military operation in Yemen against the Houthi rebels. And Randa Slim, a Syria expert at the Middle East Institute, says that Riyadh and Abu Dhabi are already both so overextended that they’re unlikely to divert troops, equipment, and money from that fight.

In fact, last December, Trump asked the Saudis for $4 billion to rebuild Syria, but Riyadh has yet to accept that proposal. That said, Saudi Arabia may send troops into Syria soon as part of the campaign to defeat ISIS. “We are in discussions with the US and have been since the beginning of the Syrian crisis [in 2011] about sending forces into Syria,” Jubeir, the Saudi foreign minister, told reporters at a press conference in Riyadh on Tuesday.

Slim also says the US would probably need Turkey’s go-ahead to send an Arab force into Syria, but that approval doesn’t seem likely to happen.

Turkish forces are currently fighting in northern Syria to establish an approximately 19-mile “safe zone” between Kurdish-controlled territory and the Turkish border. Ankara has been fighting a decades-long insurgency against Kurdish separatists inside its own country, and thus considers the powerful Syrian Kurdish forces near its border to be a looming terrorist threat.

But Syrian Kurdish forces just so happen to be working closely with US forces in Syria’s northeast to defeat what remains of ISIS. Introducing Arab forces into the mix — forces that might potentially cooperate with or even fight alongside the Syrian Kurds — would cause Ankara some serious heartburn, Jeffrey, who is now at the Washington Institute for Near East policy, explains.

“This would be Arab forces entering an Arab country without permission of its government at least potentially to cooperate with, fund, and protect a Kurdish ideological movement’s control over an Arab population,” he says, “with the goal on the part of Kurds, at least in theory, to have a base [from which] to destabilize NATO ally Turkey.”

It also doesn’t help that Ankara has a bad relationship with Riyadh and Abu Dhabi because Turkey supported the 2011 Arab Spring uprisings in countries like Tunisia and Egypt. Saudi Arabia and the UAE, on the other hand, fought to suppress those uprisings abroad and prevent similar ones from happening in their own countries.

But Turkey has also consistently called for Assad’s removal and pushed the US to do more to depose the Syrian dictator, which conceivably could make it more amenable to the idea of an Arab force interested in removing Assad getting involved in Syria.

And then there’s Egypt — one of America’s most important allies in the Middle East. Egypt supports the Assad regime. Cairo would likely be unhappy if the US backed an Arab force that went into Syria, especially if those troops started attacking Assad regime positions.

John Bolton, Trump’s national security adviser, reportedly called Egypt’s acting intelligence chief to discuss the possibility that Cairo would even contribute to the Arab force; there was no readout on how the call went. But on Tuesday, Mohamed Rashad, a former top Egyptian intelligence official, implied Egypt won’t join it. “Egypt’s Armed Forces are not mercenaries.” he said. “Egypt is adopting a strategy based on supporting the unity of Syria’s territories and its national army.”

Steven Cook, a Middle East expert at the Council on Foreign Relations, on Tuesday tweeted “Apparently the new Natl Security Advisor doesn’t know that the Egyptian government supports Assad.”

The Saudi-Iran “cold war” could turn hot

Even if an Arab force did go into Syria, it would likely do more harm than good.

Iran’s government is a Shia Muslim theocracy; Saudi Arabia’s government is a monarchy closely aligned with the country’s Sunni Muslim religious establishment. The two countries represent two ideological and political poles and have spent decades fighting each other for dominance in the Middle East and for the right to represent the Muslim world.

But instead of waging war against each other directly, Saudi and Iran back opposing political factions and extremist groups throughout the region as a way of exerting influence and control.

Iran is doing just that in Syria. Tehran has spent most of the Syrian civil war fighting to keep Assad in power while taking advantage of the conflict’s chaos to gain more control in the region. It does this in part by supporting its proxy, the militant Lebanese group Hezbollah, which is fighting in Syria on behalf of the Assad regime. On top of that, Iran’s powerful Islamic Revolutionary Guards Corps (IRGC) has established numerous military bases in Syria.

So imagine what would happen if, all of a sudden, Saudi and Emirati troops show up on the scene in Syria. “They will be in direct confrontation with IRGC, Hezbollah, and the Syrian regime,” Slim says. That means the “cold war” between the two biggest rivals in the Middle East could become an actual war.

To be fair to Trump, other US administrations had the Arab force idea too. President Barack Obama, for example, worked to rally Arab countries to do more to defeat ISIS, receiving bipartisan support for that plea. Saudi Arabia did announce a 34-nation coalition to counter ISIS in December 2015, but the US still carries most of the burden when fighting ISIS.

But just because it was an idea before doesn’t mean an Arab force is a viable idea now. “This is unrealistic, to put it mildly,” says Itani.