WASHINGTON—The frantic yet fragile diplomacy over Syrian chemical weapons veered toward an ominous impasse Thursday as President Bashar Assad added a new demand that the United States stop arming rebel forces in exchange for his regime’s compliance.

Assad’s new condition loomed as a deal-breaker in a day full of fresh twists in the diplomatic dance to avert American airstrikes.

Mere hours after Damascus filed formal paperwork with the United Nations, setting in motion the process for the surrender of toxic weaponry it has previously denied possessing, Assad told Russia’s state broadcaster more was needed to complete the transaction.

“When we see that the U.S. genuinely stands for stability in our region, stops threatening us with military intervention and stops supplying terrorists with weapons, then we will consider it possible to finalize all necessary procedures and they will become legitimate and acceptable for Syria,” Assad told RIA News.

The move suggested Assad, emboldened by the fading threat of punitive U.S. strikes, now may be bargaining not merely for his government’s survival, but for outright victory against the rebels in exchange for Syria’s chemical compliance.

In Washington, White House officials struggled to reconcile a two-track strategy, now believed to include the flow of arms to select rebel factions while simultaneously working to persuade Assad to surrender his deadliest and least conventional weapons.

“We cannot detail every single type of support that we are providing to the opposition or discuss timelines for delivery,” said White House spokesman Jay Carney.

“But it is important to note that both the political and the military opposition are, and will be, receiving this assistance.”

Secretary of State John Kerry was more blunt in describing U.S. skepticism as he began talks in Geneva with his Russian counterpart, saying, “the words of the Syrian regime, in our judgment, are simply not enough.

“This is not a game,” said Kerry, insisting that the U.S. will again weigh military options if the overtures of Russia and Syria are revealed to be stalling tactics. “It has to be real. It has to be comprehensive. It has to be verifiable. It has to be credible. It has to be timely and implemented in a timely fashion. Finally, there ought to be consequences.”

Russia has long been Syria’s primary military sponsor, supplying as much as three-quarters of the conventional weaponry that has powered Assad’s forces through two years of civil war that now has cost an estimated 110,000 lives.

The U.S., by contrast, has anguished over feeding weaponry into the fragmented rebel side amid fears of empowering factions hostile to U.S. interests. In recent weeks, however, American weapons have begun to flow, with current CIA shipments signaling a major escalation in the U.S. involvement in the war, according to the Washington Post.

The changed circumstances mean that the two primary suppliers of the conventional weaponry to Syria now also share status as the two primary negotiators in ridding Syria of unconventional weaponry.

That irony only got richer Thursday, in the furious American reaction to a provocative New York Times op-ed article under the byline of Russian President Vladimir Putin.

Positioning himself as peace-minded adherent of international law, Putin assailed the concept of American exceptionalism as “dangerous.” Putin argued for diplomacy that would end with the Assad regime’s surrender of chemical weapons while simultaneously suggesting it was Syria’s rebels, and not Assad, who bear responsibility for the Aug. 21 chemical attack on the outskirts of Damascus that triggered the crisis.

U.S. Sen. Bob Menendez captured the mood of American indignation at the article, saying he “almost wanted to vomit.” House Speaker John Boehner said he was “insulted.”

Others contrasted Putin’s enthusiastic participation in the American free press against the plight of reporters in Russia, 36 of whom have been murdered since 1992, according to the Committee to Protect Journalists.

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Others still pointed to the very different message Putin offered when last he wrote in the Times, arguing in 1999 for military intervention in Chechnya.

But the White House, for its part, carefully characterized Putin’s apparent conversion on the road to Damascus as a test the world now will watch closely. The New York Times article, it said, is a marker that puts Putin’s own reputation at stake.

“President Putin has invested his credibility in transferring Assad’s chemical weapons to international control, and ultimately destroying them,” a senior White House official told Buzzfeed. “The world will note whether Russia can follow through on that commitment.”

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