ZURICH -- A Swiss court on Tuesday rejected Oscar-winning director Roman Polanski's appeal to be released on house arrest, raising the likelihood that he would remain in jail pending legal proceedings over his possible extradition to the U.S.

In his appeal, Mr. Polanski, who is being held here in connection with three-decade-old sex charges in the U.S., extended Swiss authorities several assurances that he wouldn't flee if released. He offered as bail his luxury ski chalet in the Swiss resort of Gstaad; volunteered to surrender...