Washington  - The five-month Democratic presidential primary race between senators Hillary Clinton and Barack Obama reached the final stretch Tuesday as polls opened in South Dakota and Montana.

Opinion polls place Obama in the lead in both states.

First results were expected early Wednesday after polls close at 0100 GMT.

US media reported that Obama could declare himself the winner in the battle to become the Democratic Party's presidential candidate to go up against Republican John McCain.

Obama believes that immediately after the polls close, many of the so-called "super delegates" will announce their support for him so that he can be certain of securing the necessary 2,118 delegates to win the party nomination.

Obama would be the first black presidential candidate in US history.

It is unclear what Clinton will do. She lags behind Obama and is almost certain not to gain enough delegate votes to win.

US media have speculated that she is ready to throw in the towel as she has recalled her staffers to New York and said that she plans to make an announcement on polling night. (dpa)