WASHINGTON (AP) — The Trump administration on Friday imposed sanctions on more than 50 vessels, shipping companies and trade businesses in its latest bid to pressure North Korea over its nuclear program.

The administration billed it as the largest installment of North Korean sanctions to date.

While the number of companies from North Korea and other nations was high, the economic impact was likely to be less than previous measures that have targeted much larger financial and business networks in China and Russia that deal with the North.

The United Nations Security Council has imposed three sets of sanctions on North Korea in the past year to deprive it of revenue and resources for its nuclear and ballistic missile development. Those weapons pose an emerging threat to the U.S. mainland. The U.S. is particularly concerned about exports of North Korean coal that are prohibited by the U.N. sanctions and ship-to-ship transfers of imported oil and petroleum products.

The Treasury Department said it was barring U.S. business transactions with nine international shipping companies from China, Hong Kong, Singapore and Panama, and nine of their vessels. It also blacklisted 16 North shipping companies and 19 of their North Korean-flagged vessels.

Additionally, department designated a Taiwanese citizen, Tsang Yung Yuan, and two companies he owns or controls. Tsang was said to have coordinated North Korean coal exports with a Russia-based North Korean broker, and attempted $1 million oil deal with a Russian company sanctioned for dealing with the North.

President Donald Trump was set to call it "the largest-ever set of new sanctions" on the North in a speech Friday at the Conservative Political Action Conference, according to a senior administration official who wasn't authorized to publicly discuss the sanctions before Trump's remarks.

The announcement comes as South Korea hosts the Winter Olympics, an occasion the two Koreas have used as an opportunity to ease tensions and restart talks. Although South Korea is a close U.S. ally, animosity between Washington and Pyongyang is still running high.

Friday's action comes two weeks after Vice President Mike Pence, who attended the Olympics opening, promised the "toughest and most aggressive" economic sanctions against North Korea.

Ivanka Trump, the president's daughter and adviser, arrived in South Korea on Friday to attend the closing ceremony this weekend. 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."

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Associated Press writer Matthew Pennington contributed to this report.