Syria. (Photo credit AFP/GettyImages)
David Jackson, USA TODAY
President Obama said Friday that Syria's potential use of chemical weapons would be a "game changer," but the U.S. and its global partners must thoroughly investigate suspicions raised by intelligence agencies.
That probe will seek "more direct evidence and confirmation" of chemical weapons use, and could take a long time, Obama said before meeting with King Abdullah II of Jordan.
"This is not an on or off switch," Obama said. "This is going to be a long-term proposition."
Obama spoke as the White House aides continued to strike a cautious on claims that Syria has used chemical weapons against rebels, saying President Obama want all the facts before deciding how to proceed.
"The facts will need to be what drives this investigation, not a deadline," said White House spokesman Jay Carney.
Intelligence agencies believe "with varying degrees of confidence" that Bashar al-Assad's government has used small amounts of sarin gas in clashes with Syria rebels, officials said.
Carney said the administration is now backing a United Nations investigation into the issue to make "a definitive judgment" in the use of chemical weapons.
Also from Carney: "This is not an airtight case. We do have some evidence, but we need to build on that."
In August, President Obama said any Syrian use of chemical weapons would cross a "red line" that would prompt a U.S. response. Obama has not specified what that response might be, and neither did Carney on Friday.
"All options remain on the table," Carney said.
Other aides have warned against a rush to judgment, citing flawed intelligence about non-existent weapons of mass destruction in Iraq before the 2003 invasion of that country.