WASHINGTON (Reuters) - Hillary Clinton will hit the campaign trail for former presidential rival Barack Obama this month, making her first solo appearance on his behalf since he won their bruising Democratic nominating battle in June.

Clinton will host campaign rallies and voter registration events in Las Vegas, Nevada, on Friday and in south Florida on August 21, the Obama campaign said on Tuesday. At least the first event will be without Obama, who heads to Hawaii for a vacation that day.

Clinton, a senator from New York, appeared with Obama on June 27 at a carefully staged campaign rally in Unity, New Hampshire, where the two promised to bury the grudges from their hard-fought duel for the Democratic nomination.

The former rivals also have held joint fundraisers, in part to help Clinton pay off her remaining campaign debt.

Obama clinched the nomination in early June after the last of the Democratic primaries were completed and will face Republican John McCain in November's presidential election.

Clinton is scheduled to give a speech at the Democratic nominating convention in Denver later this month, although her chances of being named Obama's vice presidential running mate appear increasingly remote.

The Illinois senator has frequently said he is anxious for the former first lady and her husband, former President Bill Clinton, to campaign for him. It was not known whether the former president would appear with his wife at the Obama events.

(Writing by John Whitesides; Editing by David Wiessler)