WASHINGTON, May 22 (Reuters) - President Barack Obama will nominate San Antonio Mayor Julian Castro as secretary of housing and urban development and name outgoing HUD chief Shaun Donovan as his new budget director, a White House official said on Thursday night.

Obama will make the announcement at a White House event at 3:35 p.m. on Friday, the official said.

(Reporting by Mark Felsenthal and Roberta Rampton; Editing by Peter Cooney)