The Trump administration is preparing to shutter many of its immigration operations abroad, cutting back on a key support system for those applying overseas to relocate to the United States.

The director of United States Citizenship and Immigration Services, L. Francis Cissna, told senior staff members this week that the international division, which has operations in more than 20 countries, would close down by the end of the year, according to two people with knowledge of the meeting.

Agency officials said the move was intended to provide more staff resources to handle the lengthy backlog in asylum applications from tens of thousands of migrants crossing the southern border every month. But it could come at the expense of legal migration, which President Trump has said he favors: Some agency staff members said closing overseas offices will make it more difficult and time-consuming to apply to immigrate from abroad, especially for refugees already in the United States who hope to bring other family members to join them.

“This is another instance of the Trump administration halting legal immigration by denying people the opportunity to file for immigration benefits in the most expedient manner,” said Margaret Stock, a retired United States Army lieutenant colonel and an immigration attorney who frequently handles such cases.