WASHINGTON — President Trump appointed Thomas D. Homan late Monday to be the new acting director of Immigration and Customs Enforcement, an agency within the Homeland Security Department that identifies, detains, arrests and deports immigrants who are in the country illegally.

Mr. Homan has been the agency’s executive associate director of enforcement and removal operations, the division that carries out the removals. Another division, Homeland Security Investigations, has hundred of special agents who investigate fraud and other crimes.

The appointment of Mr. Homan could be seen as an indication that the president intends to carry out his campaign pledge to deport millions of undocumented immigrants and put more focus on I.C.E.’s deportation role. An executive order signed by Mr. Trump last week calls for tripling the number of deportation agents.

Mr. Homan replaced Daniel H. Ragsdale, who was the acting director of Immigration and Customs Enforcement.