The United States international is due to have a medical with a view to completing the temporary switch before the transfer window closes. Bradley is the son of United States head coach Bob Bradley and was part of their World Cup squad in South Africa last summer.
Villa boss Gerard Houllier would only say: "I don't want to say anything about it, maybe in two days' time."
But Villa sources are optimistic 23-year-old Bradley will become Houllier's fourth signing of the current window after Darren Bent, Jean Makoun and on-loan Kyle Walker.
Bradley played for the MetroStars and New Jersey in the MLS and then had a spell with Heerenveen before moving to Borussia two-and-a-half years ago.
It will further increase the already intense competition for places in the Villa midfield.
Stephen Ireland, currently sidelined with a knee injury, is being linked with a move to Newcastle.
Source: PA
Source: PA