U.S. Defense Secretary Jim Mattis showed reserve  about the existence of military options on North Korea that might spare Seoul from a brutal counterattack but declined to say what kind of options he was talking about or whether they involved the use of lethal force.

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: “Yes there are. But I will not go into details.”

Pressed on whether that might include so-called “kinetic” options that use lethal force, Mattis said: “I don’t want to go into that.”

U.S. Ambassador to the United Nations Nikki Haley previously said on  the U.N. Security Council had run out of options on containing North Korea’s nuclear program and that the United States might have to turn the matter over to the Pentagon.

Seoul is within artillery range of North Korea, which beyond nuclear and conventional weapons is also believed to have a sizable chemical and biological arsenal.