" Our military is still strong, yet our competitive edge has eroded in every domain of warfare - air, land, sea, space, and cyberspace - and is continually eroding," Fox News, reported, citing Mattis as saying.
"America has no pre-ordained right to victory on the battlefield," Mattis warned, adding at one point.
Mattis's remarks came as he unveiled the Pentagon's vision for the future detailed in a document called the national defense strategy.
The document also states that Islamic State (IS) no longer remains a top threat.
"Great power competition, not terrorism, is now the primary focus of U.S. national security. We face growing threats from revisionist powers as different as China and Russia, nations that seek to create a world consistent with their authoritarian models."
In addition to this, Mattis, a former Marine commander who has fought in Iraq and Afghanistan, said rapid technological change and America's long-running wars have diminished US military capabilities. The military was coping with "inadequate and misaligned resources."(ANI)