The United States Olympic Committee is likely to announce Thursday which city will be the U.S. candidate to host the 2024 Summer Olympics. The finalists are Boston, Los Angeles, San Francisco and Washington. An announcement would follow a USOC board-of-directors meeting Thursday at Denver International Airport. The board decided at a Dec. 16 meeting that there would be a U.S. candidate city but wanted to further evaluate the four bids. Formal application papers do not need to be filed with the International Olympic Committee until Sept. 15. The executive board will, if necessary, trim the field to about four finalists in spring 2016, and IOC members will choose the winner at their September 2017 annual meeting in Lima, Peru. The U.S. city will face formidable opposition, some spurred by changes the IOC approved eight days ago to help lower the costs of both bidding for and staging the now-gargantuan Summer Games.