American airstrikes may have mistakenly killed Syrian government forces instead of ISIS fighters, U.S. officials said on Saturday.

"We are still gathering information at this time but we have been able to confirm that earlier today, the United States struck what we believe to be an [ISIS] target," said Samantha Power, the U.S.'s ambassador to the United Nations. "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."

The Russian Defense Ministry said the American strikes south of Deir el-Zour 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.

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"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, using another name for ISIS.

"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.

An 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.

Power was also sharply critical of Russia and the Syrian government, and called the emergency Security Council meeting called by Moscow 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.

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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."

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.