The fresh support brought Obama's overall delegate total to 1,895, compared to 1,718 for his rival, Hillary Rodham Clinton. It takes 2,026 to clinch the nomination at the party convention in Denver this summer.

Edwards, who bestowed his long-sought endorsement on Obama on Wednesday, won 19 delegates before departing the presidential race in January.

Within hours, Obama picked up the backing of three of them from South Carolina and one in New Hampshire.

In addition, four superdelegates three lawmakers and a union leader endorsed Obama. Superdelegates are party leaders who may vote for anyone they like at the convention. It is essential to win their support to become the nominee because neither candidate will be able to reach 2,026 just with state votes.

"I believe now is the time to unite behind Barack Obama so we can be in the strongest place possible to win in November," Rep James McDermott said.

Rep Henry Waxman said in a statement: "I have the greatest respect and admiration for Senator Clinton and former President Clinton. It is now clear, however, that the Democratic Party is nearing a broad consensus on our nominee."