Mr Mattis discussed several aspects of the North Korea crisis in an impromptu exchange with reporters at the Pentagon, including the effect of global economic sanctions and diplomatic pressure on North Korea.
The news network reported its information comes from an unnamed official who it said to be familiar with options being discussed by the Trump administration.
Kim Jong-un has threatened to fire missiles at the island of Guam, where the USA has its foothold in the Pacific Ocean - a key strategic location.
The intermediate-range Hwasong-12 flew about 3,700 km, a longer distance than any other missile North Korea has fired, which is capable of putting the U.S. Pacific territory of Guam within range. Because the KN-17 appears to be successful, the official says the United States has assessed that it is likely North Korea will turn back to additional testing of the KN-20 (aka Hwasong 14) intercontinental ballistic missile to see if they can improve its performance.
The US has considered shooting down North Korea's missile in the past, but have never acted on it.
The US has seen no need to shoot down North Korean missiles test-fired in Japan's direction, but a future missile launch that threatens American or Japanese territory will "elicit a different response from us", defence secretary Jim Mattis has said.
China and Russian Federation have begun naval drills near North Korea amid continuing tensions over the isolated state's nuclear ambitions and ahead of a United Nations General Assembly meeting where US President Donald Trump will address the 193-member body for the first time. "But I will not go into details".
The Pentagon is looking at potential covert cyberattack options.
South Korea has raised the possibility of reintroducing nuclear weapons to the peninsula.
North Korea launched a missile over Japan last Friday, its second in the past three weeks, and conducted its sixth and by far most powerful nuclear test on September 3, in defiance of worldwide pressure.
And the situation remains tense with Mattis stating: "I believe that there is always the potential for miscalculation by the DPRK leader".