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WASHINGTON, DC - JUNE 13:  U.S. Defense Secretary James Mattis testifies before the Senate Armed Services Committee during a hearing in the Dirksen Senate Office Building on Capitol Hill June 13, 2017 in Washington, DC. Mattis and other Pentagon leaders testified about the proposed FY2018 National Defense Authorization Budget Request.  (Photo by Chip Somodevilla/Getty Images)
WASHINGTON, DC - JUNE 13:  U.S. Defense Secretary James Mattis testifies before the Senate Armed Services Committee during a hearing in the Dirksen Senate Office Building on Capitol Hill June 13, 2017 in Washington, DC. Mattis and other Pentagon leaders testified about the proposed FY2018 National Defense Authorization Budget Request.  (Photo by Chip Somodevilla/Getty Images)

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Mattis: N. Korea strike on Guam means 'game on'

Former Homeland Security Adviser to President Obama Lisa Monaco told Jake Tapper that she's concerned the war of words between the U.S. and North Korea could lead to an unintended confrontation.

Mattis: N. Korea strike on Guam means 'game on'

Former Homeland Security Adviser to President Obama Lisa Monaco told Jake Tapper that she's concerned the war of words between the U.S. and North Korea could lead to an unintended confrontation.