LONDON - A nuclear agreement between Iran and six major powers can be reached by a November 24 deadline, British Foreign Secretary Philip Hammond said on Tuesday, but Tehran needs to show more flexibility in negotiations."I believe a deal can be done," Hammond said following a London meeting with US Secretary of State John Kerry. "But we will not do a bad deal. These negotiations are extremely tough and Iran needs to show more flexibility if we are to succeed."Senior foreign officials from Iran and the six powers - the United States, Britain, France, Germany, Russia and China - gather in Vienna this week for the last round of negotiations to reach an accord that would end sanctions in exchange for curbs on Tehran's atomic program.