WASHINGTON ? President Trump on Monday officially designated North Korea as a state sponsor of terrorism, a provocative diplomatic move that he said is aimed at dramatically increasing pressure on the rogue nation to abandon its pursuit of nuclear weapons.

The president, who has repeatedly used fiery language to threaten and demean Kim Jong-un, the North Korean leader, made the announcement on Monday morning. North Korea will join Sudan, Syria and Iran as countries that the State Department identifies as ones that have “repeatedly provided support for acts of international terrorism.”

“Should have happened a long time ago,” Mr. Trump told reporters at the start of a cabinet meeting at the White House. The president said the designation will lead to new, tougher sanctions on North Korea, which he said “must end its unlawful nuclear and ballistic missile development.”

Mr. Trump has vowed to seek “complete denuclearization” in North Korea and has threatened “fire and fury” aimed at the country if it endangers the United States. The president ordered an end to the policy of “strategic patience” pursued by his immediate predecessor in the hopes that North Korea’s leader would eventually agree to negotiate.

Still, it is unclear whether the terror designation will provide the president with new and powerful leverage to force nuclear negotiations or will simply deepen the rhetorical war of words between Mr. Trump and Mr. Kim, whom the president has mockingly called “Little Rocket Man.”

Long a pariah in the international community, North Korea was put on Washington’s list of state sponsors of terrorism in 1987 after Pyongyang’s agents planted a bomb that blew up a South Korean passenger jet, killing all 115 people on board. That attack was instructed by Kim Jong-il, the late father of the current leader Kim Jong-un, according to one of the agents, who was caught alive.

North Korea was removed from the official State Department terror list nearly 20 years later by President George W. Bush, who in 2008 saw it as an opportunity to salvage a fragile nuclear deal in which North Korea would agree to halt its nuclear program.

In fact, North Korea secretly continued to develop nuclear weapons, detonating one soon after the start of President Barack Obama’s administration in 2009. That demonstrated again the regime’s refusal to abandon its nuclear program despite promises to the United States.

John R. Bolton, a former State Department official and United Nations ambassador under Mr. Bush, praised Mr. Trump for telling the truth about the nature of the regime in North Korea. “It’s exactly the right thing to do,” he said.

Mr. Bolton, who argued in 2008 against removing North Korea from the terror list, said he does not believe restoring the designation will bring Mr. Kim to the negotiating table. But he said it is “important to say what the truth is about the regime.”

Calls to put North Korea back on the list have grown since Mr. Kim’s half brother, Kim Jong-nam, was assassinated in February at Kuala Lumpur International Airport. North Korean agents were blamed for plotting the assassination, which involved the use of a rare nerve agent banned by international treaty.

North Korea has not conducted any missile tests since Sept. 15, raising cautious optimism for a possible de-escalation in the region. Mr. Trump’s decision to blacklist North Korea again, which reflects his policy of applying “maximum pressure” on the country, will likely invite angry reaction from Mr. Kim’s regime and dim chances for easing tensions on the Korean Peninsula.

The North Korean leader has a history of resorting to extreme measures against his enemies.

Since taking power after the death of his father Kim Jong-il in 2011, he has executed dozens of senior officials deemed not loyal enough, often killing them with antiaircraft machine guns, in what South Korean officials called a “reign of terror.” They said Mr. Kim probably considered Kim Jong-nam, his father’s firstborn, as his potential replacement should his regime lose control of power.

Trump administration officials had hinted in recent weeks that the president was considering adding North Korea back to the terror list in light of the country’s nuclear ambitions and the assassination earlier this year.

Speaking at the beginning of a cabinet meeting, Mr. Trump accused the North Korean government of supporting “acts of international terrorism” that justified its inclusion on the State Department’s terror list.

Mr. Trump said that the Treasury Department on Tuesday will announce new, tougher sanctions on North Korea to accompany the designation.

“It will be the highest level of sanctions,” he said.