The North has repeatedly defied the United Nations to conduct nuclear and missile tests, the latest being a mid-range missile fired over Japan on Friday, soon after the reclusive nation's sixth and most powerful nuclear test on Sept. 3.
Asked whether there were any military options the United States could take with North Korea that would not put Seoul at grave risk, Mattis said there were, but declined to give details.
"Developments in the peninsula nuclear issue up to this point prove that, no matter whether it is military threats in words or in action, they cannot promote and advance a resolution," the foreign ministry spokesman, Lu Kang, said.
"To the contrary, it just adds to tensions and makes achieving the goal of denuclearization on the peninsula appear more complicated and difficult to resolve," he added, responding to a question about Mattis' comments at a regular briefing.
Seoul is within artillery range of North Korea, which is also believed to have a sizable chemical and biological arsenal beyond nuclear and conventional weapons.
Any conflict on the Korean peninsula could lead to bloodshed unseen since the 1950-53 Korean War, which took the lives of more than 50,000 Americans and millions of Koreans and ended in an armed truce, not a peace treaty.
South Korea and the United States, and separately Russia together with China, started military drills on Monday, in a show of force against North Korea.
The Korean peninsula issue must be resolved peacefully, Chinese foreign minister Wang Yi stressed during a meeting with his Russian counterpart at the United Nations.
Chinese President Xi Jinping and U.S. President Donald Trump spoke by telephone about keeping pressure on North Korea using economic sanctions imposed through the United Nations, the White House has said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)