It is understood the 26-year-old Senegal international was due on Tyneside on Thursday, with the Magpies hoping to get their hands on a man upon whom they set their sights several weeks ago.
Former Hoffenheim frontman Ba, who is understood to have a release clause in the contract he signed with the Hammers in January, scored seven goals in 13 appearances for the Londoners last season, but could not prevent them slipping out of the Premier League.
Newcastle boss Alan Pardew put at least one striker at the top of his summer shopping list when he sat down to consider what was required at the end of last season, with Andy Carroll yet to be replaced.
Ba joined the Hammers after failing a medical at Stoke because of a knee problem, and it remains to be seen whether or not he can persuade Newcastle's doctors that his troubles are behind him.
His form during the closing months of last season suggested that is the case, but the Magpies will carry out stringent checks before putting pen to paper.
Ba's arrival in the North-East came as Newcastle skipper Kevin Nolan headed in the opposite direction with the 28-year-old midfielder expected to complete his switch to Upton Park on Thursday.
The impending departure of the club's leading scorer last season has not gone down well in certain quarters, although there is a growing realisation that owner Mike Ashley's determination to rein in expenditure is absolute.
Manager Alan Pardew was desperate to retain the services of Nolan, Joey Barton and Jose Enrique, three of his highest earners, but Nolan rejected the terms of an extension, Barton has not been offered a new deal and Enrique is yet to respond to the proposal currently on the table.
Pardew will hope the proposed capture of Ba will help to persuade supporters of the club's abiding ambition as he closes in on a series of other targets in addition to France international Yohan Cabaye.
Their pursuit of Swansea full-back Neil Taylor is also at an advanced stage, while Pardew has interests in Bayer Leverkusen's Tranquillo Barnetta and St Etienne's Blaise Matuidi, although they are among a number of players under consideration.