Obama picks Biden

CHICAGO, Illinois (CNN) - Sen. Barack Obama has selected Sen. Joe Biden as his running mate, two Democratic sources told CNN early Saturday.

The Obama campaign plans a formal announcement Saturday morning.

Biden is a veteran U.S. senator from Delaware who failed in two bids for president

News of his selection came after word that three Democrats who had been considered contenders had been ruled out. The two Democratic sources who told CNN that Obama had chosen Biden spoke on the condition of anonymity.

The Obama campaign says it plans to announce his vice presidential running mate in a text message Saturday morning. Then Obama is expected to appear with the vice presidential candidate at an afternoon rally in Springfield, Illinois.

The longtime Democratic senator was considered a possible choice for vice president, but the buzz surrounding Biden intensified after he returned this week from a two-day trip to the Republic of Georgia after Russian troops invaded.