Kim Jong-un has vowed to complete North Korea's highly-controversial nuclear weapons programme.
The enigmatic leader claimed his country was nearing its goal of military "equilibrium" with the United States - an ambition that has led to its isolation from much of the international community.
Kim's comments came after North Korea fired a ballistic missile over Japan.
The launch, condemned by Japan as "reckless", was the latest development in an ongoing crisis over the North's nuclear programme.
In recent weeks, US president Donald Trump has repeatedly warned Kim against pursuing the policy - claiming the North would be met with "fire and fury".
The missile, which travelled 2,300 miles before landing in the Pacific Ocean, was lambasted by the United Nations Security Council as "highly provocative".
Last month, North Korea fired its first missile over the country for a number of years.
Under Kim's leadership, the country has now test flown two intercontinental ballistic missiles and carried out its most powerful nuclear test to date on September 3.
North Korean media reported Kim as expressing great satisfaction over the latest launch.
He said it verified the "combat efficiency and reliability" of the missile.
The North's official Korean Central News Agency quoted Kim as declaring the missile operationally ready.
He also vowed to complete his nuclear weapons programme in the face of strengthening international sanctions, it said.
Photos showed a smiling Kim clapping and raising his fist while celebrating from an observation point shortly after the launch.
The UN accused North Korea of undermining regional peace and security.
Kim also said the country, despite "limitless" international sanctions, has nearly completed the building of its nuclear weapons force and called for "all-state efforts" to reach the goal and obtain a "capacity for nuclear counterattack the US cannot cope with."
"As recognized by the whole world, we have made all these achievements despite the U.N. sanctions that have lasted for decades," the agency quoted Kim as saying.
The leader also warned that further missile tests would be forthcoming.
The US, Russia and China condemned the North - but each suggested the other was not doing enough to resolve the situation.
Japan's UN Ambassador called the missile launch an "outrageous act" that threatened the whole world.
South Korean President Moon Jae-in, who has pushed for talks with his neighbours, said the current tests are making dialogue "impossible".
Fresh sanctions on North Korea could be imposed by the UN over the coming days.