FIFA upheld a decision last Wednesday to sanction the Catalan club for breaching rules on the international transfer of under-18 players and it means they now cannot register players in the next January and July-August 2015 windows.
The initial ban was suspended pending Barca's failed appeal, allowing the likes of Luis Suarez to be brought in during this window, but Bartomeu said they will now take the fight to get the penalty reduced to the Court of Arbitration for Sport (CAS).
"We were conscious that the ban was going to be ratified because we have committed some errors," he told Spanish television.
"We will go to CAS. We are going to work on a good defence so that in the coming months the situation can be resolved more favourably for us.
"We have a few weeks to send our motives for wanting to have the ban reduced. Often these cases end up with CAS. We recognise that we have done things badly but the sanction is very heavy."
The world governing body also rejected Barcelona's appeal against a 450,000 Swiss francs (£296,000) fine and they have been given 90 days to regularise the situation of all the minor players concerned.
Uruguay striker Suarez led a long list of recruits during the close season and Barca have especially reinforced in defence after fortunately being able to sign players before the appeal was heard.
Bartomeu said they were covering themselves in case they cannot get the ban eased, with the remaining days of this window not counting in the sanction.
"We have planned the season thinking that we could be two transfer windows without making a signing," he said.
"We have a B side with very strong players that can move up to the first team but we will see what happens with CAS and see what happens over the coming months.
"We think that the ban is out of proportion. We have signed a lot of players but we are still looking at the market and we have not closed the door on any more deals."
- Sports & Recreation
- Luis Suarez