Arsenal are waiting to hear back from Celtic after making a second bid for left-back Kieran Tierney.
The Gunners saw a £15 million ($19m) offer knocked back for the Scotland international in June and had been widely expected to return with an improved bid to try and tempt the Scottish champions into doing business.
And they have now made their move, with an offer that totals around £25m ($31m), although it is once again structured heavily with installments and add-ons to get it up to the sort of figure that Celtic have been demanding.