Defense Secretary James Mattis testified Thursday in the House Armed Services Committee (Watch live now).



Asked what worries him most about possible military action in Syria, Mattis said: "On a strategic level, it's how do we keep this from escalating out of control, if you catch my drift on that."



In his opening statement, Mattis said the world is entering "a new era of great power competition" and reiterated his promise to be trustworthy in his spending of the largest military budget in history.



It is likely Mattis will face questions about what he said at the White House Wednesday about Syria that the U.S. is still "assessing evidence" about what happened with the chemical weapons in Syria before they make a decision.





