Besiktas have been in talks with Besiktas for over a month according to BBC African football specialist Oluwashina Okeleji who confirmed that talks between the two clubs were ongoing.
“Besiktas are in advanced talks with Chelsea but nothing has been agreed with the player,” Okeleji said.
The Eagles were reported to have struck personal terms with Omeruo soon after but talks with Chelsea have dragged on.
The reason for the hold up in the transfer has been the Blues insistence on including a buyout clause option in the deal.
The 21-year-old defender was in Turkey recently after agreeing personal terms but the deal has yet to go through.
Chelsea want assurances that the Istanbul giants will sign the Nigerian international defender at the end of the season.
The Eagles meanwhile want a reduced buyout clause option which will fall in line with their budget for FFP.
The Nigerian international defender spent last season on-loan at Istanbul minnows Kasimpasa and established himself as a first team regular in one of the best performing defensive sides.