Mamadou Sakho is unlikely to play for Liverpool again this season after failing a drugs test.
The club and player agreed the France defender, 26, will remain unavailable while a Uefa investigation takes place.
Sakho had until Tuesday to request analysis of a B sample and explain the alleged presence of a prohibited substance in his system.
It is thought he tested positive for a type of fat burner, BBC Radio 5 live football reporter Ian Dennis has said.
Uefa has not opened any disciplinary proceedings against Sakho.
The player failed a drugs test after the second leg of Liverpool’s Europa League tie at Manchester United on 17 March.
Liverpool cannot comment because the process is confidential.
On Saturday, when the story broke, the club said in a statement that Sakho had not been officially suspended but he would “not be available” for selection during the investigation.
Sakho, an £18m signing from Paris St-Germain in 2013, has played 34 games for Liverpool this season, including 10 in the Europa League.