U.S. Secretary of State Rex Tillerson has declared that the U.S. policy of "strategic patience" with North Korea has ended.

He met in Seoul Friday with South Korean Foreign Minister Yun Byung-se following a visit to the Demilitarized Zone bordering the two Koreas.

Strategic patience refers to the Obama administration's policy of waiting for North Korea's regime to change its attitude toward denuclearization.

Tillerson said "all options" were on the table and the U.S. was exploring a "new range of diplomatic, security and economic measures."

He said that he doesn't believe UN Security Council sanctions were taken to the highest level, possibly signaling tighter sanctions on Pyongyang in the future.

Tillerson emphasized the United States does not want military conflict with North Korea, but that the option remains on the table if the North ratchets up its nuclear and missile threats to a level where Washington believes action is necessary.

He said the U.S. will talk with Pyongyang only when it abandons its nuclear weapons and weapons of mass destruction, adding that it is premature to talk of a nuclear freeze.

Tillerson described China's retaliation against South Korea over U.S.-provided THAAD missile defense "unnecessary and troubling," and urged Beijing to "work with us to eliminate the reason THAAD is required."

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