HITC Sport understands that deal is agreed but Man City have been considering an offer
HITC Sport reported earlier this month that Valdes had been offered to Boro - who have been looking at a number of goalkeeping options in the past few weeks.
They had shown an interest in Belgian Matz Selz, but refused to match Newcastle's offer for him with Aitor Karanka believing any new number one should be experienced.
And 34-year-old Valdes, available on a free transfer after leaving Manchester United, certainly offers that with a glittering career to date which has seen him win a host of titles with Barcelona and Spain.
Manchester City manager Pep Guardiola
HITC Sport understands that Boro have agreed terms with Valdes, believed to be a two-year contract but there has been the danger that Pep Guardiola - now in charge at Man City - could be ready to tempt him to the Etihad Stadium, having worked together at Barcelona.
Guardiola is not understood to be keen on Joe Hart or his back-up Willy Caballero, and is considering Valdes - but Boro are aware of this and will not let their deal to be stalled and have told Valdes this.
Victor Valdes at Barcelona
Boro want Valdes at their Rockliffe Park training base before the weekend and would like his signature within the next 48 hours, ahead of their opening pre-season friendly at York City this weekend.