By Steve Holland and Christine Kim
WASHINGTON/SEOUL (Reuters) - The United States said on Friday it was imposing its largest package of sanctions against North Korea, intensifying pressure on Pyongyang to give up its nuclear weapons and missile programs.
In addressing the Trump administration's biggest national security challenge, the U.S. Treasury sanctioned one person, 27 companies and 28 ships, according to a statement on the U.S. Treasury Department's website.
The actions block assets held by the firms in the United States and prohibit U.S. citizens from dealing with them.
North Korea is seeking to develop a nuclear-tipped missile capable of reaching the U.S. mainland. U.S. President Donald Trump and North Korean leader Kim Jong Un have taunted each other through the media and in August Trump threatened to go beyond sanctions by bringing "fire and fury like the world has never seen."
The Treasury's Office of Foreign Assets Control announced the sanctions, which are designed to disrupt North Korean shipping and trading companies and vessels and to further isolate Pyongyang.
Treasury Secretary Steve Mnuchin said in a statement the sanctions against the ships would help prevent Kim's government from conducting "evasive maritime activities that facilitate illicit coal and fuel transports and erode its abilities to ship goods through international waters."
The ships are located, registered or flagged in North Korea, China, Singapore, Taiwan, Hong Kong, Marshall Islands, Tanzania, Panama and Comoros, Treasury said.
Those targeted included a Taiwanese passport holder and mainland China, Hong Kong, Taiwan and Singapore shipping and energy firms.
"We imposed today the heaviest sanctions ever imposed on a country before," Trump said in an address to a conservative activist group in Washington. "And ... hopefully something positive can happen, we will see."
The United States has led an international campaign to tighten sanctions on North Korea to force it to give up its development of weapons and missiles program.
"The president is clearly frustrated and rightly so over the efforts that have failed in the past and also over the uptick in testing and the advances we've seen in the North Korean program," a senior administration official said at a background briefing for reporters.
At another briefing in Washington, Treasury Secretary Steve Mnuchin stood next to enlarged photos he said showed December 2017 images that revealed ship-to-ship transfers of fuel and other products destined for North Korea in an attempt to evade sanctions.
Mnuchin said he could not rule out the prospect of the United States boarding and inspecting North Korean ships.
He said the new sanctions are targeting virtually all shipping currently being used by North Korea. They bring the total number of U.S. sanctions against North Korea since 2005 to 450, Mnuchin said, with approximately half of those coming in the last year.
"This is very impactful," he said. "This is virtually all the ships they're using at this moment in time."
The U.S. government "also issued an advisory alerting the public to the significant sanctions risks to those continuing to enable shipments of goods to and from North Korea."
Last month three Western European intelligence sources told Reuters that North Korea shipped coal to Russia last year and that it was then delivered to South Korea and Japan in a likely violation of U.N. sanctions.
Jonathan Shanzer of the conservative Washington think tank Foundation for the Defense of Democracies said Friday's move was "the largest tranche of DPRK (North Korea) sanctions" released by the Treasury Department.
"The only thing missing here today is action against Chinese banks," he said. "We know they continue to undermine our efforts to isolate North Korea."
Harry Kazianis, director of defense studies at the conservative Center for the National Interest, said, "Cumulatively speaking, the sanctions imposed on North Korea in total since 2017 are some of the biggest ever imposed on a nation state."
Tougher sanctions may jeopardize the latest detente between the two Koreas, illustrated by the North's participation in the Winter Olympics in the South, amid preparations for talks about a possible summit between North Korea's Kim and South Korean President Moon Jae-in.
North Korea last year conducted dozens of missile launches and its sixth and largest nuclear test in defiance of U.N. Security Council resolutions. It defends the weapons programmes as essential to deter U.S. aggression.
It has been more than two months since North Korea's last missile test.
Kim said he wants to boost the "warm climate of reconciliation and dialogue" with South Korea, which hosts 28,500 U.S. troops, after a high-level delegation, including his sister, returned from the Olympics.
In an extension of that rapprochement, the North agreed on Friday to hold working-level talks on Tuesday for the Pyeongchang Winter Paralympics on the North's side of the border village of Panmunjom.
U.N. SANCTIONS
In December the United Nations approved U.S.-drafted limiting North Korea's access to refined petroleum products and crude oil, which the North Korean Foreign Ministry said amounted to an act of war. In January Washington announced a round of sanctions and urged China and Russia to expel North Koreans raising funds for the programmes.
The U.N. Security Council banned North Korean exports of coal last Aug. 5 under sanctions intended to cut off an important source of the foreign currency Pyongyang needs to fund its nuclear weapons and missile programs.
The new U.S. sanctions were announced while Trump's daughter, Ivanka, is visiting South Korea. She had dinner with Moon after a closed-door meeting with the president.
At a dinner with Moon at Seoul’s presidential Blue House, she said the purpose was also to "reaffirm our commitment to our maximum pressure campaign to ensure that the Korean Peninsula is denuclearized."
Moon said North Korea's participation in the Olympics had "led to lowering of tensions on the peninsula and an improvement in inter-Korean relations" and were thanks to President Trump's "strong support for inter-Korean dialogue."
Her visit to South Korea coincides with that of a sanctioned North Korean official, Kim Yong Chol, blamed for the deadly 2010 sinking of a South Korean navy ship that killed 46 sailors. His delegation will attend the closing ceremony and also meet Moon.
The Blue House has said there are no official opportunities for U.S. and North Korean officials to meet.
Kim Yong Chol is the vice chairman of the North's ruling Workers' Party's Central Committee and was previously chief of the Reconnaissance General Bureau, a top North Korean military intelligence agency that South Korea blamed for the sinking of its navy corvette, the Cheonan. NorthKorea has denied any involvement.