U.S. stocks finished in negative territory Thursday, with gains evaporating within the final hour of trade as markets digested a report that President Donald Trump was set to hold a news conference on China on Friday. Word of an event comes as tensions between China and the U.S. have ratcheted higher, particularly as Beijing was seen threatening the autonomy of Hong Kong. The Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA -1.51% fell 147.63 points, or 0.6%, at 25,400.64, well off its best level at 25,758.79, while the S&P 500 index /zigman2/quotes/210599714/realtime SPX -1.08% ended off 0.2% at 3,029.73 and the Nasdaq Composite Index /zigman2/quotes/210598365/realtime COMP -0.86% declined 0.5% at 9,368.99. The U.S. on Wednesday said it no longer considered Hong Kong highly autonomous under a 1992 law, a move that could lead to measures to limit Hong Kong's trade privileges and open the door to sanctions against individuals the U.S. sees as suppressing civil liberties in the territory. Also on Thursday, the governments of the U.S., Australia, Canada and the U.K. issued a joint statement reiterating their "deep concern regarding Beijing's decision to impose a national security law on Hong Kong," after China's parliament, the National People's Congress passed legislation Thursday that could greatly curtail democratic freedoms.