Video by PBS NewsHour

WASHINGTON — Defense Secretary Jim Mattis says the U.S. cruise missile strike on a Syrian air base does not signal a change in the Pentagon’s military campaign there, which is focused on defeating the Islamic State group and al-Qaida remnants.

At his first Pentagon news conference as defense chief, Mattis said the U.S. strike was meant only to demonstrate Washington’s intolerance of violations of an international convention against the use of chemical weapons. The Syrian government has denied that it used chemical arms in an attack on a Syrian town last week.

Mattis said that if Syria were to use chemical weapons again it would “pay a very, very stiff price.”

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