WASHINGTON — When President Obama first warned Syria’s leader, President Bashar al-Assad, that even making moves toward using chemical weapons would cross a “red line” that might force the United States to drop its reluctance to intervene in the country’s civil war, Mr. Obama took an expansive view of where he drew that boundary.

“We cannot have a situation where chemical or biological weapons are falling into the hands of the wrong people,” he said at an Aug. 20 news conference. He added: “A red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized. That would change my calculus.”

But in the past week, amid intelligence reports that some precursor chemicals have been mixed for possible use as weapons, Mr. Obama’s “red line” appears to have shifted. His warning against “moving” weapons has disappeared from his public pronouncements, as well as those of Secretary of State Hillary Rodham Clinton. The new warning is that if Mr. Assad makes use of those weapons, presumably against his own people or his neighbors, he will face unspecified consequences.

It is a veiled threat that Defense Secretary Leon E. Panetta repeated Thursday: “The president of the United States has made very clear that there will be consequences, there will be consequences if the Assad regime makes a terrible mistake by using these chemical weapons on their own people.”