A Swiss court has upheld a freeze on a billion dollar dividend payment to shareholders in offshore drilling group Transocean, the company said, in the wake of the US Deepwater Horizon oil spill. Transocean said the administrative court in the Swiss canton of Zug had rejected the company's appeal against a decision by the local trade registry 'to not register the first installment of the approximately 1.0 billion dollar cash distribution approved by shareholders in May 2010.' The Zug trade registry's rejection in August was down to several lawsuits filed against the compnay in the United States. The company, which owns the BP-leased offshore rig behind the worst oil spill in US history, said in a filing then that close to 250 lawsuits or claims have been filed against it in US state or federal courts. 'Transocean will determine whether or not to appeal the court's decision to the Swiss Federal Supreme Court following a detailed review of the court's reasons for the negative ruling,' it said on Friday. 'If Transocean does not appeal, the court decision will likely prevent Transocean from paying the first and all subsequent instalments of the cash distribution,' the company added. 