Newcastle United have confirmed Kevin Nolan is having a medical at West Ham after agreeing a fee for his services.
The Hammers saw an initial bid rejected by Newcastle last week, but they have now gone back with an improved offer.
The Magpies have now accepted the offer and have given the midfielder permission to hold talks with West Ham and undergo a medical at Upton Park.
Newcastle revealed earlier this month Nolan had rejected the offer of a new deal at St James' Park and they are now ready to let him leave.
New West Ham boss Sam Allardyce has made Nolan one of his top transfer targets since taking charge at Upton Park, having worked with the midfielder during his time in charge of Bolton.
Nolan enjoyed a fine season at Newcastle last term, scoring 12 goals in the Premier League, but it appears he could be swapping Tyneside for East London.
Fellow midfielder Barton expressed his surprise via Twitter, writing: "Just on my way to Ascot, feel sick."
Barton added: "Great player, leader, captain, person, trainer and mostly a friend for life. Devastated to see him SOLD".
And he added the hashtag "£mejoseandjonasnext", suggesting he, Enrique and winger Jonas Gutierrez could follow.