By Angeliki Koutantou and Lefteris Papadimas ATHENS (Reuters) - Greece must crack down on undeclared work, create more jobs, merge its pension funds and unify contribution rates to revamp its ailing pension system, a committee set up to find ways to make the system viable said on Thursday. The report had been due to be presented at the labour ministry but was moved to parliament after about 200 people protesting against a first set of pension reforms on which lawmakers will vote by Friday blocked the ministry's entrance. Greece has promised its international lenders a comprehensive pension reform plan by December.