US Secretary of State REX TILLERSON gave this indication during a visit to South Korea.
TILLERSON said the policy of strategic patience with North Korea had ended, adding that the US was exploring a new range of diplomatic, security and economic measures.
He also defended the deployment of a US missile defence system in South Korea.
The Chinese government has also criticised the move and suggested that the US and South Korea suspend their yearly military drills that always anger North Korea as a means to halt the ballistic missiles test by Pyongyang.
