Kim Jong Un
North Korean leader Kim Jong Un attends a meeting with a committee of the Workers' Party of Korea about the test of a hydrogen bomb, at an unknown location, Sept. 4, 2017. Getty Images/ STR

North Korea slammed the United States and South Korea once again after President Donald Trump placed Pyongyang back on the list of state sponsors of terrorism. North Korea's Korean Central News Agency (KCNA) on Tuesday criticized Trump for "letting out such lunatic outbursts" and said that South Korean authorities were his pets.

"The South Korean authorities is nicknamed as 'poodle' of Trump as it yields to the U.S. and creeps around the U.S. legs," KCNA said, adding that the U.S. president's outbursts are "maximizing the stand-off with the DPRK."

On Monday, Trump announced during a public meeting with his cabinet at the White House "the United States is designating North Korea as a state sponsor of terrorism. Should have happened a long time ago. Should have happened years ago." He also said the Treasury Department will announce new sanctions against North Korea on Tuesday.

Rebuking Trump's move, North Korean state media Rodong Sinmun wrote Tuesday: "The hideous crimes committed by the lunatic president of the U.S. are a blatant challenge to the dignity of the supreme leadership of the DPRK. Those who trample down and make a mockery of the DPRK's dignity can never go scot-free."

Trump's decision has heightened tensions in the Korean Peninsula, with South Korea saying its military was "maintaining a firm readiness posture" for any reaction from North Korea following the move. It has been almost two months that Kim Jong Un's regime refrained from any provocation since its testing of an intermediate-range missile over Japan in September.

However, South Korea's spy agency said Monday there was a possibility North Korea was developing an intercontinental ballistic missile capable of reaching the U.S. mainland this year. While there has been no sign of an imminent nuclear test, the North's Punggye-ri complex appears ready for another detonation "at any time," the agency reportedly told lawmakers.

"The agency is closely following the developments because there is a possibility that North Korea could fire an array of ballistic missiles this year under the name of a satellite launch and peaceful development of space, but in fact to ratchet up its threats against the United States," the lawmakers told reporters after a closed-door briefing.

Meanwhile, Chinese foreign ministry spokesman Lu Kang cautioned Tuesday the "current situation on the Korean Peninsula is highly complex and sensitive," adding that the Chinese government hoped "to see all the relevant parties do more to ease tensions, and return to the negotiating table."

As tensions escalate of North Korea developing a nuclear missile that could possibly hit the U.S., Pyongyang said Monday that Americans would regret making a "depraved and stupid guy" like Trump the president of their country.