Mr Trump said the designation of North Korea as a state sponsor of terrorism was long overdue, and he promised a new wave of sanctions as part of a “maximum pressure campaign” over the North’s development of nuclear weapons that could soon pose a direct threat to the US mainland.
North Korea will join Iran, Sudan and Syria on the blacklist.
The North had been designated for two decades until 2008 when it was removed in a bid to salvage international talks aimed at halting its nuclear efforts. The talks collapsed soon after and have not been revived since.
The primary impact of the designation may be to compound North Korea’s growing international isolation as it is already subject to an array of tough US sanctions restricting trade, foreign assistance, defence sales and exports of sensitive technology.
The step is likely to further sour relations between Washington and Pyongyang that have turned uglier with name-calling between Mr Trump and Kim Jong Un.
There is strong bipartisan support for the move in Congress, which had passed legislation in August requiring the State Department to make a determination on putting North Korea back on the list.
“In addition to threatening the world by nuclear devastation, North Korea has repeatedly supported acts of international terrorism, including assassinations on foreign soil,” Mr Trump said as he announced the designation at a Cabinet meeting at the White House.
However, the action had been debated for months inside the administration, with some officials at the State Department arguing that North Korea did not meet the legal standard to be relisted as a state sponsor of terrorism.
US officials involved in the internal deliberations said there was no debate over whether the February killing of Kim’s half brother Kim Jong Nam was a terrorist act.
Malaysian authorities have said he was killed by two women who smeared suspected VX nerve agent onto his face at Kuala Lumpur airport.
However, lawyers said there had to be more than one incident, and there was disagreement over whether the treatment of American student Otto Warmbier, who died of injuries suffered in North Korean custody, constituted terrorism.
Neither Mr Trump nor the State Department specified which acts of terrorism and assassination the North had supported. In making the announcement, Mr Trump did refer to Mr Warmbier “and the countless others so brutally affected” by North Korean oppression.
He said more sanctions would be imposed on North Korea and “related persons” that the Treasury Department would begin to announce on Tuesday - part of rolling efforts to deprive Pyongyang of funds for its nuclear and missile programmes and leave it internationally isolated.
“It will be the highest level of sanctions by the time it’s finished over a two-week period,” Mr Trump said.
The State Department said last week that Sudan, which is on the terror list itself, had agreed to cut all military and trade ties to North Korea. As the North has faced isolation from Western countries, it has increasingly sought relationships in Africa, the Middle East and South Asia in search of badly needed finances.
Evans Revere, a former senior State Department official, said North Korea is already livid with Mr Trump and is likely to react “quickly and emotionally”. A recent editorial in the ruling party Rodong Sinmum newspaper referred to the president as “a hideous criminal sentenced to death by the Korean people”.
Other analysts said Pyongyang could use the designation as a pretext for renewed weapons tests after a two-month hiatus. The latest missile test flew over Japan on September 15.
North Korea was on the terrorism blacklist for two decades after the 1987 bombing of a South Korean airliner killed 115 people. It was also accused of a 1983 bombing assassination attempt against then-South Korean president Chun Doo-hwan in Burma. The president survived, but 21 others were killed. The North has not been publicly implicated in a terror attack of that scale since.