NEW YORK (Reuters) - U.S. President-elect Donald Trump has offered retired Lieutenant General Michael Flynn the position of White House national security adviser, a senior Trump official said on Thursday.

Asked if Flynn is expected to accept, a person familiar with the offer replied: "When the president of the United States asks you to serve, there is only one answer."

Flynn, a former head of the Defense Intelligence Agency, advised Trump during the campaign on national security issues and often served as an introductory speaker at campaign rallies.

(Reporting by Steve Holland in New York and John Walcott in Washington; Writing by Eric Beech; Editing by Sandra Maler)