Source says Cory Booker will announce Senate run on Saturday

(Reuters) - Newark Mayor Cory Booker was expected to announce on Saturday he will run for U.S. Senate in New Jersey in a Democratic primary set for August to fill the seat of the late Sen. Frank Lautenberg, a source close to Booker said on Friday.

The campaign staffer asked to remain anonymous because he was unauthorized to speak publicly about the announcement.

Booker had previously announced his intention to seek Lautenberg's seat in 2014.

After Lautenberg's death on Monday, New Jersey Governor Chris Christie called a special election to fill the remainder of Lautenberg's term.

Christie on Thursday appointed the state's attorney general Jeffrey Chiesa, who like Christie is a Republican, to fill the seat until the general special election in October. Chiesa said he would not compete for the seat in the special election.

Booker, mayor of the state's most populous city, is among New Jersey's best-known and most popular Democrats.

(Reporting by David Jones; Editing by Edith Honan, Daniel Trotta and Nick Zieminski)

[Newark, New Jersey Mayor Booker speaks with L.A. Mayor Villaraigosa after Booker addressed first session of the Democratic National Convention in Charlotte]