Atletico Madrid will not be able to sign players in the January window as they continue to contest a Fifa ban.
The Spanish side – and rivals Real Madrid – were banned last January from registering players for two windows for breaching rules over the transfer of players under 18.
However both were allowed to continue to make signings while they appealed.
But Atletico have now agreed to “waive its right to seek the suspension of the ban for the winter transfer period”.
Cas will make a final decision by 1 June after Atletico’s first appeal – to Fifa in September – failed.
A club statement, which reiterated that they are “completely unmoved in its position that the transfer ban is unjustified”, said it was “to ensure a procedural calendar that allows Atletico Madrid to fully present its appeal, while giving Cas sufficient time to thoroughly consider all the arguments”.
Real are still allowed to sign players in January.
La Liga champions Barcelona were given the same punishment for the same offence in April 2014 and were banned from signing players in both 2015 windows after failing in their appeals to Fifa and Cas.