Chelsea have taken their appeal against a two-window transfer ban to the Court of Arbitration for Sport.
Fifa has banned the Blues from signing players until the end of January 2020 and the club failed with their first appeal to the world governing body.
It followed an investigation into their signing of foreign under-18 players.
The transfer window closes on 8 August and the Court of Arbitration for Sport (Cas) said “it is not possible” to say when it will make a decision.
Chelsea have not asked for the ban to be lifted while Cas considers its decision.
They signed United States winger Christian Pulisic from Borussia Dortmund for £58m in January, before their ban was imposed in February.
Real Madrid’s bid to sign the Blues’ Belgium forward Eden Hazard for a fee of about £88m is expected to be concluded in a matter of days.