The Gunners are on the verge of completing the signing of the 22-year-old fullback ahead of Deadline Day.

Arsenal and Celtic have reached an agreement for the transfer of left-back Kieran Tierney. The 22-year-old defender is set to become the most expensive Scottish player-ever after with his side finally accepting the Gunners' £25 million offer.

Tierney has reportedly been on the radar of the Unai Emery's side all summer with the club aiming to bolster its defense ahead of the new season. Talks progressed steadily over the last few weeks and a breakthrough was finally made on Wednesday after the Premier League outfit has two initial bids rejected.

According to the Sky Sports, Tierney is expected to arrive in London on Wednesday night to conclude his medical before the transfer window closes on Thursday. The left-back, who last played for Celtic on 4 May as a result of an injury, is expected to sign a five-year-contract.

At the age of 22, the Scottish full-back has made 170 appearances across all competitions for Celtic having made his debut in 2015. During his stint, he won four league titles, two Scottish Cups and two League Cups for The Bhoys.

Meanwhile Arsenal is expected to complete its transfer window with the signing of a center-back. In the last couple of days, the Emery's side has been heavily linked with moves for RB Leipzig's Dayot Upamecano as well as Juventus' Daniele Rugani.

Reports that emerged from England on Wednesday indicated that both deals will be difficult to complete, forcing the Gunners to turn their attention to Chelsea's David Luiz. The Brazilian center-back is said to have boycotted training in a bid to force a move to Emirates before Thursday's 5pm transfer deadline.