WASHINGTON: US Democratic presidential candidate Barack Obama has chosen his Senate colleague, Joseph Biden, as his vice-presidential running mate, CNN television reported on Saturday. ( Watch ) The network cited unnamed Democratic Party sources, but did not offer any details. Earlier, ABC News said a detail of Secret Service agents had been sent to assume Biden's protection in preparation for his possible new role as an official candidate for high office. Biden, 65, emerged on top after Obama, according to unidentified sources, broke the news to two other contenders -- Indiana Senator Evan Bayh and Virginia Governor Tim Kaine -- that they were no longer under consideration. The chairman of the Senate Foreign Relations Committee, Biden would bring decades of national security experience on board, having first been elected to Congress at the age of 29 in 1972. On the campaign stump this week, Obama has singled out Biden for praise over his response to the crisis in Georgia and proposals to extend more US economic aid to Afghanistan.