Source: U.S. Growing Confident of Chemical Attack in Syria.
BLITZER: Disturbing new images from Syria suggest the regime of President Bashar al Assad may have launched another chemical gas attack possibly in retaliation for the downing of a Russian helicopter. Our global affairs correspondent Elise Labott is working the story for us. Elise, you are learning more information?</s>ELISE LABOTT, CNN GLOBAL AFFAIRS CORRESPONDENT: That's right, Wolf. Tonight, a senior U.S. official tells me the administration is growing confident that a chemical attack, likely chlorine, took place near Aleppo. Now, the Russians are blaming the opposition, but the official said the claim is not critical because the opposition does not have air power and the attack took place from the sky. And it's all raising a lot of questions tonight about whether Moscow can be trusted.</s>TRUMP: If we could get Russia to help us get rid of is, if we could actually be friendly with Russia, wouldn't that be a good thing?</s>LABOTT (voice-over): Donald Trump's solution to defeating ISIS in Syria hinges on warmer ties with Russia and its leader Vladimir Putin. But on the ground, Russian air strikes are helping regime forces tighten their grip on Aleppo and today U.S. officials are investigating claims of a poisonous gas attack on U.S.-backed rebels. Chilling video footage shows men gasping for breath.</s>JOHN KIRBY, STATE DEPARTMENT SPOKESMAN: If it's true, it would be extremely serious.</s>LABOTT: Russia denies any involvement, but the gas attack was eerily close to the downing of a nearby Russian military helicopter hours earlier. Rebel forces cheering around the flaming wreckage of a chopper which Russia says was delivering humanitarian aid. This weekend, Russian airstrikes a third hospital in Aleppo, and with more than 6,000 dead or injured in the last few months and another 300,000 trapped without aid, a humanitarian catastrophe is unfolding.</s>JOHN KERRY, SECRETARY OF STATE: It is critical, obviously, that Russia restrain both itself and the Assad regime from conducting offensive operations. Nobody's going to sit around and allow this pretense to continue.</s>LABOTT: Hillary Clinton has backed President Obama's plan to fight ISIS in Syria with air strikes and aid from moderate rebels, but allegations and Russian intelligence hacked Democratic Party computers and meddled in the U.S. election are fueling fresh concerns that Moscow cannot be trusted and could derail a controversial deal in the works for the U.S. and Russia to share intelligence on ISIS and other terrorists in down strikes against opposition targets. President Obama says his eyes are open, but the alleged hacking isn't his first concern.</s>BARACK OBAMA, PRESIDENT OF THE UNITED STATES: If, in fact, Russia engaged in this activity, it's just one on a long list of issues that me and Mr. Putin talked about, that I've got a real problem with. That's not going to stop us from trying to make sure that we can bring a political transition inside of Syria that can end the hardship there.</s>LABOTT: And growing concern tonight that a Russian offer to let residents of Aleppo leave the city is just a ruse to attack the rebels as they flee. Growing concerns tonight, Wolf, that Moscow's promises across the board are not really anything that the U.S. can count on.</s>BLITZER: Elise Labott at the State Department, thank you. That's it for me. Thanks very much for watching. "ERIN BURNETT OUTFRONT" starts right now.