The exercise comes more than a week after North Korea launched four ballistic missiles into the sea off Japan's northwest coast, with one rocket landing about 200 km (124 miles) from the town of Oga.
Tillerson outlined a tougher strategy to confront North Korea's nuclear threat after visiting the world's most heavily armed border near the tense buffer zone between the rivals Koreas.
Analysts have also suggested that North Korea is in the process of building a facility for nuclear tests that are greater in magnitude than those the country has conducted in the past.
Secretary Tillerson will travel next to Beijing in an effort to convince President Xi to use his country's economic leverage to pressure North Korea into giving up its weapons program. That coalition included Japan, Russia, South Korea, and China, which served as the host country. "We will be having discussions with China as to further actions we believe they might consider taking that would be helpful to bringing North Korea to a different attitude about its future need for nuclear weapons", he explained previously.
Washington has been pressing Beijing to do more to rein in North Korea's nuclear and missile programmes.
President Donald Trump called out North Korea for its bad behavior in an early morning tweet Friday.
The US Secretary of State has arrived in South Korea for the second leg of an Asian tour focusing on finding a "new approach" for North Korea. "We do not control them, and we have strongly opposed North Korea's development of nuclear weapons from the very beginning", he said, referring to the North's official name, the Democratic People's Republic of Korea.
While Tillerson's refusal to restart talks with North Korea maintains standard USA policy on the matter, his suggestion that America consider military action against the rogue nation is risky break from status quo.
So does Trump have some new formula for success? The North conducted two nuclear test explosions and 24 ballistic missile tests previous year. The Korean War ended with an armistice, not a peace treaty, which means the Korean Peninsula remains in a technical state of war.
- The U.S. and South Korea are now holding their biggest-ever annual joint military exercises, which are seen by the North as a dress rehearsal for invasion.
Meanwhile, the liberal bloc expressed caution about his signal of a tougher US approach to the North.
The region is in diplomatic meltdown as China is furious with the installation of the Terminal High Altitude Area Defense (THAAD) system, created to defend against North Korean missiles. Washington says the manoeuvrs are routine and defensive.