"This brings up the total to over 450 sanctions that we have on North Korea", Mnuchin said Friday.
"Hopefully, something positive can happen".
The United Nations Security Council has imposed three sets of sanctions on North Korea in the past year.
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 global waters.
North Korea athletes joined with those from the South during the games in a sign of easing tensions. We work closely with the Federal Bureau of Investigation and they give us the new information.
The designations fit into the administration's larger strategy of economically and diplomatically isolating North Korea in an effort to drive it to denuclearize.
But the new sanctions' effectiveness depends on whether they can successfully be implemented. The U.S. imposed $12 billion in fines on European banks for money laundering for Iran but has yet to impose a fine on any Chinese bank for similar actions on behalf of North Korea. "May be very, very unfortunate for the world".
South Korean President Moon Jae-in highlighted to Trump how the Olympics have served as a vehicle for dialogue between the two Koreas, and said the US and South Korea should make use of the current mood of rapprochement between the Koreas in seeking denuclearization.
The Security Council slapped three sets of sanctions on North Korea previous year: one on August 5, aimed at the iron, coal and fishing industries; another on September 11, squeezing textile trade and oil supplies; and the latest on December 22, targeting refined petroleum products.
The US Treasury Department announced a new raft of sanctions on Friday in an attempt to target entities linked to North Korea's shipping and trade sectors.
The latest US sanctions on the North come after Ivanka Trump landed in South Korea Friday and met with President Moon Jae-in at the Blue House, reaffirming Washington's commitment to its "maximum pressure campaign to ensure that the Korean Peninsula is denuclearized".
The export breakdown by product comes after data on Friday showed trade with North Korea fell to the lowest level in dollar terms on records going back to June 2014.
"We are very excited to attend the 2018 Winter Olympic Games to cheer for team U.S. and to reaffirm our strong and enduring commitment with the people of the Republic of Korea". "We expect people to follow through on the obligations of the United Nations sanctions and our sanctions programs". The United States and Asian allies will expand ship interceptions to prevent sanctions violations, USA officials said. Its continued illicit ship-to-ship oil transfers, the official said, represent an effort to "make up that difference".
In addition to her presence at the Olympics' closing ceremony Sunday, a high-level North Korean delegation will also attend.
China "demands the U.S. side immediately stops such relevant mistaken actions to avoid harming bilateral co-operation in the relevant area", the ministry said in a short statement on Saturday.
Mnuchin said the sanctions hit "virtually all the ships they're using at this moment in time".
Experts believe North Korea has the capability to launch a missile that could reach Washington, but it's unclear whether it has the technology to fit a nuclear warhead onto such a missile.