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In the first few weeks of the Trump administration, some senior figures began floating a new plan: President Trump's improved relations with Moscow would help the White House force a split between Russia and Iran, both staunch allies of Syrian President Bashar al-Assad.

"If there’s a wedge to be driven between Russia and Iran, we’re willing to explore that," said a senior administration official to the Wall Street Journal's Jay Solomon in February about the "emerging strategy."

But a few weeks later, it's clear that the White House has neither the diplomatic savvy nor the conditions on the ground needed to create such a wedge. The American airstrikes launched last week against a Syrian airfield has ratcheted up the tension between the United States and Russia. The strike was intended to deliver a "message" to Assad and his allies that the United States will no longer tolerate chemical weapons attacks on civilians, but it has also rallied Assad's patrons around him.

The joint command center that coordinates Russian and Iranian forces — as well as other militias fighting for the Assad regime — issued a statement on Sunday saying the United States had crossed its own "red line" by bombing the Syrian government air base.

"What America waged in an aggression on Syria is a crossing of red lines," read the statement. "From now on we will respond with force to any aggressor or any breach of red lines from whoever it is and America knows our ability to respond well." The Russian military has also shut down its hotline to U.S. forces, which the two countries used to keep their aircraft in Syria out of each others' way.

While this is very likely symbolic bluster, top Iranian and Russian officials have indeed conferred after the U.S. strike. Unsurprisingly, they don't seem ready to shift their strategy in Syria.

Meanwhile, the White House is ratcheting up the rhetorical pressure on the Kremlin. "I think what we should do is ask Russia, how could it be, if you have advisers at that airfield, that you didn’t know that the Syrian air force was preparing and executing a mass murder attack with chemical weapons?" said Trump's national security adviser, H.R. McMaster, on Fox News. U.S. officials also told the Associated Press on Monday that Russia probably had advance knowledge of last week's chemical weapons strike, something Moscow denies.

This all means that Secretary of State of Rex Tillerson, who will visit Moscow this week, is probably in for an awkward trip. As my colleague Carol Morello reported, Tillerson still intends to push for Russia to distance itself from Assad, even if there's little chance of success.

"This is a big cold shower," said Samuel Charap, a Russia analyst with the Rand Corp., to Morello. "Even if behind closed doors they might engage on other issues in a more pragmatic manner, the public posture is going to be one of emphasizing how they disagree about [Syria]. [Vladimir] Putin is not going to want to be seen as chummy with the U.S. secretary of state."

The idea of coaxing Russia away from Iran is "certainly not going to go anywhere now," said Alex Vatanka, an Iran expert at the Middle East Institute in Washington. Indeed, he said, "the opposite result has been achieved."

In many respects, Iran and Russia aren't natural allies. There's much that divides them, not least hundreds of years of historical rivalry. Both countries are energy exporters vying for similar markets. Both governments harbor larger ambitions of geopolitical dominance in the Middle East. And, of course, there are always going to be limits to any alliance between the Islamic republic and a Russian leadership partially animated by a brand of Christian nationalism.

"Russia is hardly interested in Iran’s so-called Axis of Resistance, which stretches from Iran to Iraq, Lebanon, and Syria and essentially consists of Shia forces," noted Mohsen Milani in Foreign Affairs last year. "Given its ambition to become a great power in the Middle East, it cannot alienate the Sunni countries. Nor is Russia interested in antagonizing Israel. In fact, relations between Israel and Russia are exceptionally friendly."

But Russia and Iran need each other in Syria to buttress Assad. "The glue is their common enmity toward the United States" and Washington's imperatives in the region, Vatanka said.

"At the moment, it is going to be difficult to drive a wedge between Russia and Iran," wrote Anna Borshchevskaya of the Washington Institute for Near East Policy in February. "Too many interests hold them together." And after the events of the past few days, those bonds seem even harder to unwind.

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