The Treasury Department said it was barring USA business transactions with nine worldwide shipping companies from China, Hong Kong, Singapore and Panama, and nine of their vessels.
The United States also proposed a list of entities to be blacklisted under separate UN sanctions, a move 'aimed at shutting down North Korea's illicit maritime smuggling activities to obtain oil and sell coal'.
The U.N. Security Council has unanimously boosted sanctions on North Korea since 2006 in a bid to choke off funding for Pyongyang's nuclear and ballistic missile programs, banning exports including coal, iron, lead, textiles and seafood, and capping imports of crude oil and refined petroleum products. "Those who trade with North Korea do so at their own peril", Mnuchin said. Washington is particularly concerned about exports of North Korean coal that are prohibited by the United Nations sanctions and ship-to-ship transfers of imported oil and petroleum products.
The officials said the USA -led initiative, which has not been previously reported, shows Washington's increasing urgency to force North Korea into negotiations over the abandonment of its weapons programmes.
"North Korea, we imposed today the heaviest sanctions ever imposed by our country before". It alerted industries to North Korea's "deceptive shipping practices", which includes falsifying the identity of vessels and disabling transponders that track ships' movements.
Tighter sanctions plus a more assertive approach at sea could dial up tensions at a time when fragile diplomacy between North and South Korea has gained momentum.
In a terse statement, China's foreign ministry said the government had always fully and thoroughly enforced United Nations resolutions on North Korea, and absolutely did not allow any of its citizens or companies to contravene them.
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He said foreign countries put pressure on him not to move the embassy and begged him, "Don't do it, don't do it". The date was chosen to coincide with 70th anniversary of Israel's independence.
Japan also supported the new sanctions, Defence Minister Itsunori Onodera said, according to the Kyodo news agency.
A senior administration official told reporters that these designations are a critical part of the US' maximum pressure campaign to diplomatically and economically isolate North Korea. At a dinner with South Korean President Moon Jae-in, she reaffirmed "our commitment to our maximum pressure campaign to ensure that the Korean Peninsula is denuclearized".
Ivanka Trump, the president's daughter and adviser, arrived in South Korea on Friday to attend the closing ceremony this weekend.
The Treasury Department, in conjunction with the State Department and the U.S. Coast Guard, is issuing a global shipping advisory meant to alert the world to North Korea's "deceptive shipping practices", the official said.
North Korea past year conducted dozens of missile launches and its sixth and largest nuclear test in defiance of UN Security Council resolutions.
In an extension of that rapprochement, the North agreed to hold working-level talks for the Pyeongchang Winter Paralympics on the North's side of the border village of Panmunjom.