US President Barack Obama has said new allegations of chemical weapons use by Syrian forces are of "grave concern".
In an interview with CNN he said the allegations this week by opposition forces are more serious than previous charges against the regime of President Bashar al-Assad.
Earlier U.N. Secretary-General Ban Ki-moon said he's "troubled" by allegations that chemical weapons were used in an attack near Damascus.
Opposition groups claims more than 1-thousand people died in the incident on Wednesday.
The Assad regime denies involvement.
In this mornings interview Mr Obama stopped short of saying point blank the United States believes such weapons were used -- an act that would cross what he has previously called a "red line".
He says the government is now gathering information.