The Trump administration has quit participating in talks on a proposed United Nations agreement to improve ways of handling global flows of migrants and refugees, describing it as a subversion of American sovereignty.

The administration’s decision to renounce the talks on the agreement, the Global Compact on Migration, was announced in a statement Saturday night by the United States Mission to the United Nations, surprising migrant-rights advocates who called it shortsighted and counterproductive.

Many said the decision appeared to reinforce what they called an atmosphere of renewed American isolationism and exceptionalism at the United Nations in the first year of the Trump White House.

Trump administration officials said the decision was not an American repudiation of cooperation with other countries but a rightful defense of the government’s power to determine who can enter the United States.