UEFA's experiment of using two extra match officials is to be extended to the Champions League and qualifying games for the 2012 European Championship.
The use of an extra official behind each goal was first tried out in the Europa League last season and will be used in Europe's second-tier knockout competition again from the group stage next season.
In the Champions League, the extra officials will first appear in the playoff round in August, UEFA announced Thursday.
Football's rule making body agreed earlier this month to extend trials for two more years.
The International Football Association Board also told national football authorities they are free to run experiments in their domestic competitions if they want.