Celtic have made a second bid for key transfer target Vasilios Barkas, according to reports in Greece.
The Scottish champions had their initial offer of around £3.2million rejected for the Greek international by AEK Athens.
Celtic returned have returned with a €4.5million offer report Greek newspaper Ora ton Spor.
Barkas has emerged as a significant figure in the club’s transfer window with no progress on a Fraser Forster return and Craig Gordon having departed on a free contract. It has meant Scott Bain has been left as the sole first-team goalkeeper.
The 26-year-old, who has 10 caps for the Greek national side, was linked with Celtic earlier in the year and has reported interest from Leeds United.
AEK Athens are understood to want £6.5million for the goalkeeper having rejected a €5million last summer from French side Montpellier.
Celtic begin their quest for 10 in a row on Sunday when they host Hamilton Academical. Their preparations continued with a 2-0 win over Ross County on Sunday and they are set to face Hibs on Monday afternoon in another pre-season friendly.