Celtic say they are "disappointed and frustrated" that they have not yet been given permission to install rail seating at their stadium.
However, the club are still hopeful they can gain the necessary approval of the Health and Safety Executive.
The club indicated its intention to explore safe standing last year.
"The Safety Advisory Group (SAG) has asked for further time and information to be provided before a final decision can be made," read a Celtic statement.
There is provision in Scottish Professional Football League rules for rail seating. Currently, the 12 top-flight clubs have all-seater grounds.
Standing areas have proven popular since their introduction to the Bundesliga in Germany.
Clubs in England, including Aston Villa, are also exploring the idea of safe standing.
The Celtic statement added: "The club has provided detailed information in support of this proposal over the past two years and has made every effort to address comprehensively all issues raised by the SAG.
"The club of course will provide the additional information requested and we will undertake to do this as quickly as possible. We will then seek an early meeting of the SAG to consider progressing this matter without further delay.
"This is an important spectator safety issue. It is also an opportunity for Glasgow and for Scottish football to lead the UK in this area and it is one which Celtic will continue to pursue.
"We look forward to the next meeting taking place and hope this matter can be resolved as soon as possible."