The Wearside club had been looking to sign Borini on a permanent deal since last summer, having enjoyed a positive loan spell with the Black Cats in the 2013/14 season.
He retuned to Liverpool last term in an attempt to break into Brendan Rodgers’ first-team set-up, but the 24-year-old Italian forward managed just 18 appearances in all competitions for the Reds.
A summer transfer was expected this year, and Sunderland were always looking at bringing him back to the Stadium of Light.
However, they almost missed out on signing Borini, due to West Ham making a late approach for him.
The Hammers submitted an offer to Liverpool for the striker whilst he was on Wearside undergoing a medical with Sunderland, but Borini rejected the approach immediately as he always wanted to return to the Stadium of Light.
West Ham’s search for a new striker is not a secret, with head coach Slaven Bilic keen to bring in a new forward due to many of his attacking options being struck down with injury.
Borini would have been a solid signing, with a respectable goal record, Premier League experience, and still with youth on his side, but missing out on him means the Hammers are looking to complete another signing before the close of the transfer window later today.