U.S. Democratic presidential candidate Senator Barack Obama (D-IL) smiles during a town hall-style meeting at Troy High School in suburban Detroit, June 2, 2008. (Xinhua/Reuters Photo)

U.S. senator Barack Obama is set to make history Tuesday night to become the first African-American to be a major-party's presidential nominee.

At present, Obama is only 10 delegates short of reaching the threshold of 2,118 delegates needed to clinch the nomination.

Thirty one delegates are at stake in the final contests under way in South Dakota and Montana, where Obama is set to take at least 10 delegates.

However, his remaining rival, senator Hillary Clinton, does not plan to concede the race Tuesday night, according to her campaign chairman Terry McAuliffe.

Two New York lawmakers said Clinton expressed willingness during a conference call to serve as Obama's running mate in November.

But in a statement issued Tuesday afternoon, her campaign said there was nothing new in her remarks.

"Today on a conference call with New York legislators, Sen. Clinton was asked whether she was open to the idea of running as vice president and repeated what she has said before: She would do whatever she could to ensure that Democrats take the White House back and defeat John McCain," it said.

Superdelegates are the approximately 800 Democratic party leaders and officials who vote in the delegate nominating process. Around 200 of them have yet to endorse either Obama or Clinton.

Former President Jimmy Carter and Rep. James Clyburn, the No. 3 Democrat in the House and the highest ranking African-American in Congress, were two of the most prominent superdelegate endorsements that Obama picked up.

Obama is holding a rally at the Xcel Energy Center in Saint Paul, Minnesota, the same arena which will house the 2008 Republican National Convention in September.

Clinton will spend the evening at a campaign event in New York.

Editor: Yan