Government conflict-of-interest rules forced the private equity executive to bow out of consideration for the post.
Mattis's remarks may come as a blow to hopes of increased cooperation between the two powers following the election of President Donald Trump to the White House.
In a complicated week for US relations with Russia, a Russian surveillance ship was spotted off the eastern seaboard.
In his trip to Asia this week, US President Donald Trump's defense secretary, retired Marine General James Mattis, is expected to look at South Korea's moves to host a Terminal High Altitude Area Defense (THAAD) system to defend against North Korea's missile capabilities.
James Mattis, a retired general nominated for secretary of Defense, does not meet the requirement that secretaries have been retired from the military for seven years. Why some Democrats may give him a pass.
At a 'thank you' tour stop in North Carolina on Tuesday, the president-elect promised to get Congress to waive restrictions that would keep the recently retired general from serving as Defense secretary.
In a speech at the Reagan National Defense Forum in Simi Valley, Calif., Defense Secretary Ashton Carter stressed the need for US and allied forces to ensure that the Islamic State does not reemerge.
Shinzo Abe's trip to Hawaii comes six months after President Obama became the first sitting president to visit Hiroshima.
Americans are more open to torture than several of its allies and enemies, according to a new report. What does that say about how the US sees global conflict?