Obama has 264 party leaders who have said they will vote for him at the Democratic convention, while Clinton has 267, CNN reported.
One of the new Obama backers, Rep. Donald Payne of New Jersey, was previously a Clinton supporter.
Because of the closeness of the race, the superdelegates could be critical to the nomination. They include major elected officials, some union leaders and leaders in other groups.
The other new additions to the Obama camp were Ed Espinoza, a Democratic National Committee member from California, Rep. Peter DeFazio of Oregon and John Gage, president of the American Federation of Government Employees. All had been uncommitted.