Story highlights John Bolton is set to endorse Mitt Romney for president

Bolton was former President George W. Bush's permanent U.N. representative

John Bolton, the former U.S. permanent representative to the United Nations, is set to endorse presidential candidate Mitt Romney, a source close to Romney's presidential campaign said Wednesday.

Bolton served in the administrations of former Presidents Ronald Reagan and George H.W. Bush before former President George W. Bush appointed him the U.N. role.

Bolton endorsed Sen. John McCain's presidential bid in February 2008.

Bolton's endorsement of Romney was first reported by the Wall Street Journal.