"Let me be very clear. The policy of strategic patience has ended. We are exploring a new range of diplomatic, security and economic measures. All options are on the table," Tillerson told reporters during a joint news conference with South Korean Foreign Minister Yun Byung-se on Friday.
"Certainly we do not want to, for things to get to military conflict," Tillerson said.
However, he went on to say that "if they (North Korea) elevate the threat of their weapons program to a level that we believe requires action, then, that option's on the table."
He added that a "comprehensive set of capabilities" is being developed to deal with the country.
Tillerson's comments were made after visiting the demilitarized zone that divides the two Koreas.
It comes just three days after the North's state news agency KCNA warned the US of "merciless" attacks if America’s nuclear-powered aircraft carrier ‘USS Carl Vinson’, which arrived in South Korea to take part in annual drills, infringed on its sovereignty during the exercises.
"If they infringe on the DPRK's (Democratic People's Republic of Korea's) sovereignty and dignity even a bit, its army will launch merciless ultra-precision strikes from ground, air, sea and underwater," the news outlet said, RT reported.