South Korea was quick to respond Tuesday to North Korea's threats that it would use nuclear weapons on hostile foes and that the country planned to continue to work toward building its arsenal. The South's government pledged it would take stern action against Pyongyang with the cooperation of the United States and its allies in the international community, reported the Korea Times.

"A possible missile launch or nuclear test by North Korea are serious provocations and military threats," said Ministry of Unification spokesman Jeong Joon-hee during a press conference, according to the Korea Times.

The United Nations Security Council prohibits North Korea from carrying out test launches, and Joon-hee said the South would work with allies to reign in North Korea. "Seoul will sternly respond to them by collaborating with the international community. We are closely working together with the United States on the matter," he said, according to the Korea Times.

Pyongyang's newest threat came Tuesday, when it said the country would not hesitate to use nuclear weapons against the U.S. and others if they pursue "their reckless hostile policy" toward North Korean leader Kim Jong Un's regime, according to CNN. An atomic energy official said the country has improved its arsenal in both quality in quantity in a statement released through the North's state-run Korean Central News Agency.

"If the U.S. and other hostile forces persistently seek their reckless hostile policy towards the [Democratic People's Republic of Korea] and behave mischievously, the DPRK is fully ready to cope with them with nuclear weapons any time," the director of the North Korean Atomic Energy Institute said, according to CNN. 

The North further insisted it would launch so-called satellites, which the West considers missile testing, on long-range rockets Oct. 10 to mark the ruling communist party's 70th anniversary. It also said it had restarted production at its bomb fuel plants. 

Amid the new threat, South Korea has ramped up diplomatic efforts to gain international support to put pressure on the North. "The international community should send Pyongyang a message with one voice that its nuclear program is unacceptable," Second Vice Foreign Minister Cho Tae-yul said during a keynote speech at the annual International Atomic Energy Agency meeting Tuesday, according to the Korea Times. He pushed that the North should be forced to scrap all existing nuclear efforts.

The White House responded to the North's statements Tuesday, condemning Pyongyang and saying it would not accept the country as a nuclear state. "We urge North Korea to refrain from actions and rhetoric that threaten regional peace and security. And focus instead on fulfilling its international obligations and commitments," said White House spokesman Josh Earnest, according to USA Today.