WASHINGTON (Reuters) - U.S. Treasury Secretary Jack Lew on Thursday urged top German and French officials to hammer out a debt deal with Greece that will ensure Athens is able to pay its debts. Lew "underscored the importance of achieving debt sustainability in the upcoming negotiations," a Treasury official said of Lew's meetings in Europe, which included a meeting with German Finance Minister Wolfgang Schaeuble in Berlin and French Finance Minister Michel Sapin in Paris. Lew also met with European Central Bank President Mario Draghi in Frankfurt, the official said. ...