The independent site RealClearPolitics.com has Mr Obama leading Mrs Clinton in the delegate count 1,137 to 1,134 ahead of the Nov 4 presidential election.

This includes pledged 'superdelegates' - party luminaries, usually top elected officials and former officials. So far, 213 have pledged support for Mr Clinton and 139 for Mr Obama.

Of the 796 superdelegates, 444 remain uncommitted. However, under party rules even the pledged superdelegates can change candidates if they please.

Analysts say the superdelegates are likely to throw their support behind the candidate who seems to be winning in the run-up to the national Democratic party convention in late August, to avoid a divided conference.

A total of 2,025 delegates are needed to win the Democratic nomination for president. -- AFP