Celtic rejected an opening bid of £15m last month but this latest development will further test their resolve.
Napoli remain interested in Tierney but have still yet to sell current left back Mario Rui to finance the deal.
Arsenal have returned with a second offer worth up to £25million for Celtic’s Kieran Tierney
Carlo Ancelotti is a big admirer of the Scotland international and is still hopeful of beating Arsenal to his signature.
Unai Emery needs defensive reinforcement and Arsenal hope their latest offer will prove enough.
Tierney, currently struggling with a pelvic injury, feels the time is right to leave the Scottish champions this summer.
Their first bid for the left-back was rejected but they hope new offer will test Celtic’s resolve