Arsenal have agreed a £32.67million deal in principle with Real Sociedad to sign midfielder Mikel Merino.
The initial fee is £28.43m, with a further £4.24m in add-ons. The 28-year-old has agreed a four-year contract with the option of a further year, subject to passing a medical.
The Gunners, who fell the wrong side of a two-horse race for the Premier League title against serial champions Manchester City last season, have already bolstered their ranks this summer with the arrival of ex-Bologna defender Riccardo Calafiori.
But having identified midfield as a key area to strengthen ahead of the summer transfer deadline, Arsenal have been in advanced talks with LaLiga outfit Real Sociedad in an effort to lure the Spaniard to the Emirates.
Merino returned to Sociedad this summer off the back of Spain's triumph at the European Championships in Germany, with Spain beating England 2-1 in the final.
The Sociedad midfielder is set to arrive on a four-year contract, with the option of a fifth year
The 28-year-old will likely partner England midfielder Declan Rice in the engine room, with Thomas Partey remaining a superb squad option following his appearance during Arsenal's 2-0 win over Wolves on the opening weekend.
Kai Havertz performed the No 8 role at times for Arsenal last season but has since found a purple patch of form leading the line for the Gunners, emerging as Arteta's clear first-choice centre forward.
Merino has played 242 times for Real Sociedad over the past six years, while he has also racked up 28 caps for La Roja.
Mail Sport reported last week how a £30m bid should be enough to sign the 28-year-old and Arsenal sporting director Edu had been in Spain to push negotiations along ahead of the start of the new Premier League season.
Merino - who has one year left on his contract - was excluded from Real Sociedad's squad for their LaLiga opener against Rayo Vallecano on Sunday, with Sociedad boss Imanol Alguacil saying that was 'the best solution' amid the transfer speculation.
Should Merino's move materialise, he will become Arsenal's second signing of the window after Riccardo Calafiori, who joined the north London club from Bologna earlier this summer
The progress on the Merino deal comes at a time when Arsenal are close to selling Eddie Nketiah to Nottingham Forest for £30m.
The Gunners academy graduate has scored 38 goals in 168 games for the club and Mail Sport reported on Monday how Arsenal had rejected Forest's initial £25m bid.