U.S. President Donald Trump on Friday announced what he said was the "largest ever" set of sanctions against North Korea, as part of what the White House bills as its "maximum pressure" campaign against Pyongyang.
"We have imposed the heaviest sanctions ever imposed," Trump said during a speech to the Conservative Political Action Conference in Washington.
WATCH: Trump on North Korea Sanctions
The sanctions, which target North Korea's illicit shipping and trade, came despite a recent thaw in tensions between North and South Korea, which have been holding high-level talks.
The sanctions target 56 entities — 27 shipping and trade companies, 28 vessels and one individual — located all over the world, from North Korea to China to Tanzania, according to senior U.S. administration officials.
North Korea has long relied on a complex and shadowy global shipping network to evade U.N. sanctions that target its nuclear and ballistic missile programs.
"We are determined through these efforts to increase the pressure on the North Korean regime and show Kim Jong Un that there's no other path for him to take but denuclearization," said a senior U.S. official.
The announcement came as Trump's daughter and senior adviser, Ivanka Trump, arrived in South Korea for meetings with senior Seoul officials and to attend the closing ceremony of the Winter Olympics.
At a dinner for the U.S. delegation in Seoul, South Korean President Moon Jae-in praised North Korea's participation in the Olympic Games "as an opportunity for us to engage in active discussions between the two Koreas, and this has led to lowering of tensions on the peninsula."
"I also believe that such developments are thanks to President Trump's strong support for inter-Korean dialogue, and I would like to express my deep appreciation on this point as well," Moon said.
A high-level North Korean delegation is also attending the closing ceremony, but U.S. officials have said there will not be any meetings between the U.S. and North Korean delegations.
Since Trump took office, U.S. officials have given mixed messages on the idea of talking with the North — at times suggesting Washington is open to talks without preconditions and at other moments insisting Pyongyang must first commit to giving up its nuclear program.
The latest U.S. position, outlined by Vice President Mike Pence, is that the White House remains open to negotiations but that it will also keep up its campaign to diplomatically and economically isolate North Korea.
Since last August, the U.S. has helped oversee three rounds of U.N. Security Council sanctions against North Korea. The pressure has not stopped Pyongyang from conducting more nuclear and missile tests.
Nonetheless, Treasury Secretary Steve Mnuchin told reporters that U.S. sanctions were "beginning to have a significant impact" on North Korea's ability to fund its weapons programs, though he did not provide any evidence for the assertion.
The U.S. on Friday also released a global advisory intended to alert the world to "deceptive shipping practices used by North Korea to evade sanctions," according to a Treasury Department statement.
"The president has made it clear to companies worldwide that if they choose to help fund North Korea's nuclear ambitions, they will not do business with the United States," said Mnuchin.
But the new sanctions' effectiveness depends on whether they can successfully be implemented.
And the U.S. has limited leverage over many of the shipping companies involved in helping North Korea evade sanctions, warned Gary Samore, former White House coordinator for arms control and weapons of mass destruction.
"A lot of the companies working with North Korea are very small," Samore said. "And they don't care whether they work with the United States."
Jonathan Schanzer, a former Treasury Department official, praised the new sanctions for addressing North Korean shipping, which he said "has long been a gaping hole in the U.S. sanctions regime."
"The only thing missing here today is action against complicit Chinese banks," said Schanzer, now with the Foundation for Defense of Democracies. "We know they continue to undermine our efforts to isolate North Korea.
"Until we take that step, DPRK will be able to operate rather freely in the formal financial sector."