Frank Lampard is expected to be unveiled as Chelsea's latest signing after the London club called a 4pm press conference at Stamford Bridge.
The England midfielder has been in negotiations with Chelsea after they agreed an £11m fee with West Ham for the 22-year-old's services.
If the news is confirmed, it comes on the day Glenn Roeder was named as the new manager of the Hammers, with the 45-year-old admitting his disappointment at losing a player of Lampard's calibre.
Lampard decided to leave Upton Park last month following his father Frank snr's departure in the wake of former West Ham manager Harry Redknapp's decision to quit the club.