US President Donald Trump said on Monday he was designating the Democratic People's Republic of Korea (DPRK) as a state sponsor of terror.

Trump said in a cabinet meeting in White House that "we will be instituting a very critical step, and that will start right now. Today, the United States is designating North Korea as a state sponsor of terrorism."

"It should have happened a long time ago. It should have happened years ago," said Trump, accusing the DPRK of "threatening the world by nuclear devastation" and repeatedly supporting "acts of international terrorism, including assassinations on foreign soil."

White House officials previously blamed the Asian nation for killing a man in a Malaysia airport and murdering the US citizen Otto Warmbier, both denied by Pyongyang.

Warmbier was an American university student who, while visiting DPRK as a tourist in Jan. 2016, was arrested and sentenced to 15 years imprisonment. He was released in June 2017 and died six days after he returned to the United States.

"As we take this action today, our thoughts to turn to Otto Warmbier, a wonderful young man," Trump added, vowing to impose further sanctions and penalties on Pyongyang and related persons.

Trump also said the US Treasury Department will announce measures on Tuesday to slap an additional "large" sanction against the DPRK.

"It must end its unlawful nuclear and ballistic missile development, and cease all support for international terrorism -- which it is not doing," he noted.

The DPRK was removed from the list of state sponsors of terror by President George W. Bush in 2008.