Washington  - Senator Barack Obama on Monday had passed rival Hillary Clinton in support from the Democratic Party leaders known as super delegates who will be key in choosing the party's presidential nominee.

Obama already led in the total number of delegates needed to secure the party's nomination at a convention in August. But neither candidate has clinched the 2,025 total delegates needed, and the small number of state-by-state contests left mean the super delegates, who decide independently of delegates pledged by voters, will be key in the outcome.

A CNN count showed Obama taking the lead among super delegates on Monday with 274 to Clinton's 273, erasing what was once her significant lead among the party leaders. About 200 super delegates remain undecided with a handful of contests left. A separate count by website realclearpolitics. com puts Obama ahead by four.

The candidates face off in a primary on Tuesday in West Virginia, where Clinton is expected to win by wide margins on support from the white, working-class voters who have provided the backbone of her support in recent contests. (dpa)