United States President Barack Obama said allegations of chemical warfare in Syria constitute a "big event of grave concern," in an interview with CNN released Friday.
The US has not yet confirmed that toxic gases were employed in Syria, as Syrian activists have claimed, but Obama had previously warned that such actions would cross a "red line."
"Has that red line now been crossed?" BBC News asked on Thursday, referring to accusations that Syrian President Bashar al-Assad's government used chemical weapons to kill over 1,100 people in a poison gas attack earlier this week.
Syria is in the midst of a brutal civil war pitting Assad's forces against an armed rebellion in violence believed to have killed over 100,000 people in the past two and a half years.
This is not the first time chemical warfare has been reported in Syria, but Obama said the latest developments could prove "very troublesome" and "require America's attention," according to the Associated Press.
A top US official told The Wall Street Journal on the condition of anonymity on Wednesday that Washington is inclined to believe chemical weapons were indeed used recently in Syria.
"There are strong indications there was a chemical weapons attack — clearly by the government," the official said.
Obama told CNN that the Syrian government is not likely to be forthcoming on the issue, despite prodding by Russia, a close ally of Assad.
Russia has reportedly urged Assad to cooperate with the UN team currently in Syria to investigate previous alleged incidents of chemical weapons use. Foreign Minister Sergei Lavrov spoke with US Secretary of State John Kerry, agreeing that an objective investigation was needed.
However, Obama told CNN's "New Day" anchor Chris Cuomo in an exclusive interview released on Friday, "We don't expect cooperation [from the Syrian government], given their past history."
The US leader said "core national interests" are at play in the Syrian conflict, "both in terms of us making sure that weapons of mass destruction are not proliferating, as well as needing to protect our allies, our bases in the region," according to CNN.