WASHINGTON (MCT) — President Barack Obama on Monday for the first time threatened U.S. military intervention in Syria’s civil war, warning the beleaguered regime of President Bashar Assad against breaching a U.S. “red line” of moving or using chemical or biological weapons.

Addressing a news conference, Obama indicated that his administration believes that Assad could resort to chemical or biological weapons to stave off his overthrow and that Islamic extremists allied with the rebels could acquire such weapons if they were deployed.