WASHINGTON (Reuters) - Republican Jeff Sessions will become the first sitting U.S. senator to endorse party front-runner Donald Trump on Sunday evening, Drudge Report said, marking another in a string of high-profile endorsements for the billionaire businessman.

Sessions' support will top the list of politicians who have thrown their backing to Trump in the last week, including Republican U.S. Representatives Chris Collins of New York and Duncan Hunter of California, as well as former rival for the nomination New Jersey Governor Chris Christie, who endorsed on Friday.

(Reporting by Alana Wise; Editing by Cynthia Osterman)