美股三大股指高开低走，标普500指数转跌，道指跌幅扩大至0.63%，纳指涨幅收窄至0.46%。

Group 1 - The three major U.S. stock indices opened higher but experienced a decline, with the S&P 500 index turning negative [1] - The Dow Jones Industrial Average's decline expanded to 0.63% [1] - The Nasdaq's gains narrowed to 0.46% [1]