Arsenal remain optimistic of agreeing a deal for Celtic's Kieran Tierney after seeing their opening bid of £15million rejected, BBC Sport's David Ornstein reports.

The Gunners' first offer was turned down by the Scottish champions, but the left-back will seemingly be sold for the right price, with Arsenal expecting a compromise to be reached eventually.

After an acceptable fee is agreed, Arsenal will have to agree on terms with the 22-year-old, but that is not expected to prove difficult.

He may well be eager to test himself in the Premier League after emerging as one of the stars of the SPFL. 

Why do Arsenal want Tierney?

Tierney is one of the most highly-regarded players in a record-breaking Celtic side, and there has long been an acceptance that he was bound for a higher level. 

He has been with Celtic since the start, joining their youth setup fourteen years ago.

He made his debut for the senior team in 2015 and has since racked up 170 appearances for the Hoops.

More than forty of those outings, notably, have come in European competition. 

Tierney's career tally of 37 assists indicates that he fulfils the attacking expectations placed on the modern full-back.

He has twelve caps for Scotland and has been included in their national team of the year three times.

The Isle of Man-born defender also has a hat-trick PFA Scotland Young Player of the Year awards under his belt.

Arsenal are looking to bolster the defensive line after shipping 51 goals in the league last season, but their budget is limited.

Indeed, Ornstein reported before last month's Europa League final that Unai Emery would have only £40million to spend should he fail to secure Champions League football.

Tierney would represent a shrewd acquisition in such circumstances and would be expected to compete with Sead Kolasinac for a starting role.