According to a letter sent to members of the organization on Monday, the Justice Department has informed European officials that the United States is withdrawing from a multinational group that was formed to investigate leaders responsible for the invasion of Ukraine, such as Russia’s President Vladimir V. Putin.

The decision to withdraw from the International Center for the Prosecution of the Crime of Aggression against Ukraine, to which the Biden administration was a part in 2023, is the latest sign of the Trump administration’s move away from President Joseph R. Biden Jr.’s commitment to holding Mr. Putin personally accountable for crimes committed against Ukrainians.

This group was created to hold accountable the leadership of Russia, along with its allies in Belarus, North Korea, and Iran, for a category of crimes defined as aggression under international law and treaties that violate another country’s sovereignty and are not initiated in self-defense.

The U.S. authorities have informed me that they will conclude their involvement in the ICPA by the end of March,” said Michael Schmid, president of the group’s parent organization, the European Union Agency for Criminal Justice Cooperation, known as Eurojust, in an internal letter obtained by The New York Times.

The group remains committed to holding those responsible for core international crimes in Ukraine accountable.

The United States was the only country outside of Europe to send a senior prosecutor to The Hague to work with investigators from Ukraine, the Baltic States, Poland, Romania, and the International Criminal Court.

A department spokesman did not immediately respond to a request for comment on Sunday night.

The Trump administration is also reducing the work done by the department’s War Crimes Accountability Team. This team was created in 2022 by then-Attorney General Merrick B. Garland and was staffed by experienced prosecutors. Its purpose was to coordinate the Department of Justice’s efforts to hold Russians accountable for atrocities committed following the full invasion three years ago.

“There is no hiding place for war criminals,” Mr. Garland said when the unit was established.

The department added that it will pursue every avenue of accountability for those who commit war crimes and other atrocities in Ukraine.

During the Biden administration, the team, known as WarCAT, played an important supporting role. It provided Ukraine’s overburdened prosecutors and law enforcement with logistical support, training, and direct assistance in bringing charges of war crimes committed by Russians to Ukraine’s courts.

The team was responsible for one significant case. In December 2023, U.S. prosecutors used a war crimes statute for the first time since it was enacted nearly three decades ago to charge four Russian soldiers in absentia with torturing an American who was living in the Kherson region of Ukraine.

In recent comments, President Trump has aligned closer to Mr. Putin while clashing with Ukraine’s president, Volodymyr Zelensky, contending that Ukraine played a role in provoking Russia’s brutal and illegal military invasion.

“You should have never started it,” Mr. Trump said in February, referring to Ukraine’s leaders. “You could have made a deal.” He followed up in a post on social media, calling Mr. Zelensky a “Dictator without Elections” and saying he had “done a terrible job” in office.

The Trump administration gave no reason for withdrawing from the investigative group other than the need to redeploy resources, according to sources familiar with the situation who spoke on the condition of anonymity because they were not authorized to discuss the moves publicly.