SEOUL/BEIJING — North Korea on Sunday slammed the latest US measures against it as an “act of war”, after US President Donald Trump announced the “heaviest sanctions ever” on the nuclear-armed regime.

The measures, which Washington says are aimed at forcing Pyongyang to roll back its banned nuclear and weapons programs, target more than 50 North Korea-linked shipping companies, vessels and trade businesses.

“Like we have said repeatedly, we consider any restrictions on us as an act of war,” the North’s foreign ministry said in a statement carried by the state-run KCNA news agency.

It also vowed a retaliation if the US “really has the nerves” to confront the North in a “rough” manner.

Trump warned on Friday that, if the latest sanctions don’t work, the US would “go to phase two” that “may be a very rough thing”, without elaborating.

In response, the North also vowed to “subdue the US in our own way” if provoked, saying “Trump is trying to change us with such sanctions and hostile remarks, which shows his ignorance about us”.

“We already have our own nuclear weapon — a treasured sword of justice to protect us from such threats from the US,” the foreign ministry said.

The comment came hours before the North’s senior delegation led by Kim Yong Chol, a blacklisted military general, is set to attend the closing ceremony of the South’s Winter Olympics, which will also be attended by Trump’s daughter Ivanka Trump.

Meanwhile, Beijing has protested against Washington’s decision to impose sanctions against Chinese companies accused of conducting illicit economic deals with North Korea, the foreign ministry said.

“China is strongly opposed to the United States’ long-arm jurisdiction and unilateral sanctions on Chinese entities and individuals,” foreign ministry spokesman Geng Shuang said on Saturday.

“We have lodged solemn representations to the United States and asked the US to immediately cease the wrong practice so as to avoid undermining relevant cooperation between the two sides,” he added.

China, North Korea’s only major ally, has steadfastly rebuffed Washington’s calls for a full oil embargo — fearing the chaotic collapse of the Pyongyang regime — but has accepted caps agreed at the United Nations.

“We will never allow Chinese citizens or companies to be engaged in activities that violate resolutions from the United Nations Security Council,” Geng said.

But Washington says its latest measures target entities that have helped Pyongyang evade UN sanctions.

In another development, South Korean President Moon Jae-in on Sunday met a senior North Korean delegation led by a blacklisted general before the Winter Olympics closing ceremony.

The visit by Kim Yong Chol, heading an eight-member delegation that crossed the Demilitarized Zone Sunday morning, is the final piece of the Games-led diplomacy that has dominated headlines from Pyeongchang after months of tensions.

But the visit by Kim, accused of masterminding past attacks on the South, has sparked angry protests from conservatives.

Moon met Kim for about an hour beginning 5 p.m. (0800 GMT) in Pyeongchang, the presidential office said without elaborating.