Boris Johnson rules himself out to be next British PM

Ex-London Mayor Boris Johnson on Thursday ruled himself out of the race to be the next Conservative leader and prime minister of the United Kingdom.

In a speech in London -- billed as his campaign launch -- Johnson said he did not believe he could provide the leadership or unity needed.

Johnson's statement comes after Justice Secretary and fellow Brexit campaigner Michael Gove's surprise announcement that he would run for leader.

Home Secretary Theresa May is also among the candidates. Nominations shut at noon.