US President Barack Obama says the US has concluded that the Syrian government carried out a chemical weapons attacks near Damascus.
He said the use of chemical weapons affected US national interests and sending a "shot across the bows" could have a positive impact on Syria's war.
But in the interview with PBS, he said he had not yet made a decision about whether to intervene militarily.
His comments follow a day of behind-the-scenes wrangling at the UN.
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