U.S. Defense Secretary Mark Esper on Thursday said the U.S. still sees a "political agreement" as the best path forward with North Korea, urging its leader Kim Jong-un to exercise "restraint."

Esper made the remarks in an interview with Fox News when asked about U.S. President Donald Trump and his administration's plans regarding North Korea issues.

Esper said that the best path forward is still a political agreement on denuclearizing North Korea and that the U.S. wants to remain on that path, urging Kim and his leadership team to sit back down at the negotiation table to do that.

The Pentagon chief, however, made clear that the U.S. military stands ready to "fight tonight" if necessary. He said that the U.S. has a full array of forces, South Korean partners and a broader set of partners as well, adding he's confident in the readiness of forces to deter North Korean bad behavior.

The remarks came after the North Korean leader threatened to abandon a self-imposed moratorium on nuclear and long-range missile tests and reveal a "new strategic weapon" soon.