WASHINGTON — Seeking to further isolate North Korea, the Trump administration on Friday announced a broad new raft of economic sanctions against 56 companies, ships and people around the world that allegedly aid the government in Pyongyang in pursuing its nuclear ambitions.

President Donald Trump, who was supposed to personally describe the sanctions in a major speech to conservative activists, instead only briefly mentioned them at the close of his address. He called the measures the “heaviest sanctions ever imposed on a country before.”

The details were left to the Treasury Department, which said the measures were aimed at disrupting North Korean shipping and trading companies believed to illegally use vessels, sometimes disguised under foreign flags, to transport forbidden goods such as fuel and possible weapons material.

The administration “is aggressively targeting all illicit avenues used by North Korea to evade sanctions,” Treasury Secretary Steven Mnuchin said in a statement. If companies or individuals anywhere in the world “choose to help fund North Korea’s nuclear ambitions, they will not do business with the United States,” he added.

North Korea is already subject to scores of sanctions both from the United States and the United Nations and other world powers, aimed at halting dictator Kim Jong Un’s development of nuclear weapons. The penalties have failed, however, to stop North Korea from making progress toward its stated goal of developing a nuclear-armed ballistic missile capable of hitting U.S. territory.

The new sanctions target 28 vessels located or registered in North Korea, China, Tanzania and Panama. Satellite imagery purportedly shows North Korean vessels conducting ship-to-ship transfers of oil, coal and refined petroleum products with vessels under foreign flags, to circumvent U.N. sanctions prohibiting such practices.

Shutting down these boats, Mnuchin said, “will significantly hinder the Kim regime’s capacity to conduct evasive maritime activities that facilitate illicit coal and fuel transports, and erode its abilities to ship goods through international waters.”

Also targeted are 28 shipping and trading companies that work in or with North Korea, Treasury said.

One individual was added to the blacklist, Taiwanese citizen Tsang Yung Yuan, whom Treasury accused of coordinating North Korean coal exports with a Russia-based North Korean broker.

Previously, individuals under sanction have included Chinese bankers and Russian businessmen.

Sen. Ed Markey of Massachusetts, the senior Democrat on the East Asia Subcommittee of the Senate Foreign Relations Committee, echoed many critics in saying the new sanctions, while welcome, do not go far enough.