In response to North Korea's latest act of military aggression against Japan, the U.S. military, South Korea and Japan conducted air drills on Monday with live weapons.

The U.S. and South Korean planes practiced attacks by releasing live weapons at a firing range in South Korea, according to the U.S. Pacific Command. The drills involved American bombers and stealth jets, and South Korean and Japanese warplanes.

The drills come three days after North Korea fired a missile over Japan, and are the latest indicator that North Korea's weapons programs are advancing. The country flight-tested two intercontinental ballistic missiles in July.

South Korea F-15K combat planes, U.S. Air Force B-1B bomber planes and F-35B combat planes drop bombs to hit simulated targets during a drill in South Korea, on Sept. 18. (South Korea Defence Ministry/EPA-EFE)

Experts say it's only a matter of time until Kim Jong-un achieves his stated objective of possessing reliable nuclear-tipped missiles capable of striking anywhere in the mainland U.S.

On Saturday, state media quoted Kim as saying that North Korea's final goal "is to establish the equilibrium of real force with the U.S. and make the U.S. rulers dare not talk about military option" for the North.

South Korea divided

South Korea's new Defence Minister Song Young-moo visits the demilitarized zone dividing the two Koreas on July 15, 2017. (Yonhap South Korea/EPA)

The liberal-leaning government of President Moon Jae-in said it has no intention of requesting that the U.S. bring back tactical nuclear weapons. On Monday, South Korean Defence Minister Song Young-moo told lawmakers that it is "not proper" to reintroduce U.S. nuclear weapons. He previously said the idea should be "deeply considered" by the allies, inflaming already heated debate on the issue.

Alarmed by North Korea's advancing weapons programs, many conservatives in South Korea have called for the reintroduction of U.S. tactical nuclear weapons in the South.

China pushes back

China's Communist Party newspaper on Monday criticized the United States for demanding that Beijing put more pressure on North Korea to rejoin its weapons programs.

"The so-called 'China's responsibility theory' is essentially moral kidnapping," the People's Daily said in a commentary. It also noted that sanctions should not harm "legitimate economic and trade exchanges between North Korea and the outside world" and the lives of everyday people.

China accounts for about 90 per cent of North Korea's trade and sends largely free crude oil shipments to the North. Beijing has been increasingly frustrated with North Korea's nuclear drive, but it still doesn't want the North to collapse and cause a wave of refugees to cross the border into China and American troops to move into North Korea.

Chinese Foreign Ministry spokesperson Lu Kang has called on the U.S. and North Korea to end counterproductive military rhetoric. (Nicolas Asfouri/AFP/Getty Images)

China's foreign ministry said Monday that military threats being made by North Korea and the U.S. were counterproductive.

"Some related parties keep sending threatening messages both in words and deeds that include warnings of military actions to each other," ministry spokesman Lu Kang told reporters at a regular briefing.

"But actually, these kinds of actions didn't help solving the problem but further complicate the situation, which do no good to the resolution of the peninsular issue."

Instead, he said, the international community should strictly implement the sanctions imposed on North Korea by the UN Security Council.