North Korea's ruler Kim Jong-un wants to make his country the most powerful nuclear power in the world.

Kim said building nuclear forces is the most important goal, state news agency KCNA reported on Sunday.

"The end goal is to have the strongest strategic armed forces in the world, the absolute strongest armed forces that have not existed in this century," Kim said.

The recent test of a long-range missile would have shown that North Korea has the crucial skills to build the strongest army in the world.

He called the Hwasong-17 missile the most powerful strategic weapon in the world.

It shows North Korea's determination and ability to build the strongest army in the world.

Scientists have made a "wonderful leap in the development of technology for mounting nuclear warheads on ballistic missiles," Kim said, without giving details.

Cooperation offer from China

The day before, KCNA had reported on an alleged offer of cooperation from Chinese President Xi Jinping to Kim.

In a message to Kim, Xi said Beijing is ready to work with Pyongyang for "regional and world peace, stability, development and prosperity."

Xi went on to say he is willing to cooperate with the North Korean leadership while "changing the world" and "history in unprecedented ways."

The KCNA cites Xi's response to Kim's congratulations to the Chinese leader on his third term as general secretary of the Communist Party.

North Korea had intensified its missile tests after joint military exercises by South Korea and the United States.

UN Security Council members condemned the recent launch of an ICBM.

However, they refrained from making a formal statement due to resistance from China and Russia.

The US government believes that the key to Pyongyang's backing down lies with China, the country's most important ally.

According to a senior US official, Washington wants to ask Beijing to use its influence over the country.