National security adviser John Bolton warned the Syrian regime not to take the United States' new stance on Syria as a "change in our position that any use of chemical weapons would be met by a very strong response," Reuters reports.

Why it matters: A U.S. withdrawal from Syria raises concern about unchecked aggression in the region by Syrian President Bashar al-Assad, Iran, Russia and of course ISIS. While the White House has made clear that overthrowing the Assad regime was not a military objective, Bolton said the Syrian dictator should "be under no illusions" that the U.S. would not take action against the use of chemical weapons, as it did earlier this year.