WASHINGTON — The U.S. Treasury will announce on Thursday sanctions on 17 Saudis for their role in the killing of journalist Jamal Khashoggi at the Saudi consulate in Istanbul, according to a source familiar with the administration's plan. Those to be sanctioned include Saud al-Qahtani, a former top aide to Crown Prince Mohammed bin Salman, as well as the Saudi Consul General Mohammed Alotaibi, the source said.