U.S. President Barack Obama on Sunday left Washington for Nevada, where he will remain for the next three days, prepping for the first presidential debate against Republican challenger Mitt Romney next Wednesday.

According to White House schedule, Obama's only public event is a campaign rally at a high school in Las Vegas Sunday evening, and he will be in Henderson, Nevada, for the remainder of the next three days.

Media reports have noted that Senator John Kerry has been playing Romney in mock debate sessions against Obama, but aides said Obama hasn't gotten enough practice because of the demands of being president.

Just like Obama, Romney's schedule is also light in the next few days. His public schedule before Wednesday includes only a rally in Denver, Colorado on Monday, according to his campaign.

Romney is being aided by Ohio Senator Rob Portman in mock debates. Portman plays Obama in those sessions to sharpen Romney's responses.

Romney is behind Obama in polls, and with the election only a little over a month away, he needs to do well in the debates to change the status of the race.

Obama and Romney will hold three debates through October, and Vice President Joe Biden and Romney's running mate Paul Ryan will also meet for one debate.