The Trump administration said Thursday it plans to allow only 18,000 refugees to resettle in the United States in the 2020 fiscal year, the lowest number in the history of the modern refugee program.

In a move immediately decried by immigrant advocates as an affront to the nation's humanitarian commitments, the administration said it had to shift focus to processing a backlog of hundreds of thousands of asylum claims, most of which are filed by migrants from Central America crossing the U.S.-Mexico border.

"The current burdens on the U.S. immigration system must be alleviated before it is again possible to resettle large number of refugees," the State Department said in a statement.