The U.S. military said a coalition airstrike officials believed were against the terror group ISIS in Syria was halted Saturday after Russian officials said it was possible the targets were part of the Syrian military.
U.S. officials told NBC News "it is possible" that U.S. airstrikes mistakenly struck Syrian military forces in the operation south of Dayr Az Zawr.
The Russian defense ministry claims the American strikes killed 62 Syrian soldiers and wounded 100 in four separate airstrikes. U.S. officials could still not confirm those numbers or whether Syrian armed forces had actually been killed in the strike.
"Coalition forces believed they were striking a Daesh fighting position that they had been tracking for a significant amount of time before the strike," U.S. Central Command said in a statement, referring to another name by which ISIS is known.
"Syria is a complex situation with various military forces and militias in close proximity, but coalition forces would not intentionally strike a known Syrian military unit," the statement said.
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The apparently errant strike could deal a crushing blow to a fragile U.S. and Russian-brokered cease-fire that has largely held for five days despite dozens of alleged violations on both sides. The cease-fire, which does not apply to attacks on ISIS, has already been the subject of disputes between Moscow and Washington, with each accusing the other of failing to fully implement it.
The United Nations Security Council has scheduled an emergency meeting for Saturday night at Russia's request to discuss the airstrike.
U.S. ambassador to the United Nations Samantha Power said Saturday that the attack was immediately halted upon being informed that the strikes may have been hitting Syrian military vehicles and troops.
"If we determine that we did indeed strike Syrian military personnel, that was not our intention and we, of course, regret the loss of life," she said. The U.S. is investigating the incident.
But Power was sharply critical of Russia and the Syrian government, and called the emergency Security Council meeting a "stunt." She accused Russia of being silent in the face of the use of airstrikes, chemical weapons and torture by the government of Syrian President Bashar al-Assad.
"A meeting like this, a stunt like this, isn't helping anybody," she said.
Russia's representative to the U.N., Vitaly Churkin, accused the U.S. of violating the cease-fire, and questioned the timing of the U.S. airstrike in the area. "She was not interested in what I have to say ... so there is no point in listening to Ambassador Power," Churkin said.
The Russian ministry of defense said in a statement earlier that "In case the airstrike is caused by faulty target coordinates, it is a direct consequence of the American side's stubborn reluctance to coordinate with Russia their anti-terrorist operations in Syria."
But a senior U.S. defense official told NBC News the U.S. military had gone "above and beyond" the requirements under the current memorandum of understanding between the U.S. and Russia when it informed the Russian military in advance they were about to strike what was believed to be an ISIS target.
The military received no information from the Russians that Syrian forces were operating in the area, the official said.
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The area where the strike was conducted has been struck by coalition forced in the past, Central Command said in the statement.
It is not uncommon for U.S.-led coalition forces to confer with Russian officials "as a professional courtesy and to deconflict Coalition and Russian aircraft," but it is not required by a current agreement on flights in Syria.
The U.S. defense official told NBC News that it's reasonable to assume "the Russians may try to exploit the incident" for propaganda purposes.