West Ham United have opened negotiations with Chelsea to land the signature of Kurt Zouma, Sky Sports reports.
The Hammers are keen on signing a central defender as they look to adjust to the additional workload of Europa League football.
They have been linked with several players including James Tarkowski, but Zouma has now emerged as the top transfer target.
The club are prepared to offer £20 million for the France international, but the Blues are likely to demand much more.
The west London giants recently attempted to include Zouma as a makeweight to sign Sevilla centre-back Jules Kounde.
The approach has been unsuccessful. They are still reluctant to lose Zouma on the cheap, and could demand around £30m.
Spurs are prepared to pay £40m for Romero. A deal appears unlikely with Atalanta unwilling to accept less than £50m.