North Korea raised the stakes in a war of words late Tuesday with its military threatening to strike the U.S. territory of Guam in a pre-emptive operation, according to media reports. Citing North Korea's state media, Reuters and Dow Jones reported a spokesman for North Korea's military said it is carefully examining an operational plan to launch missiles at Guam, where the U.S. has several military bases. The threat from North Korea comes after President Donald Trump said North Korea faces "fire and fury" if it continues with its threats. After a choppy day of trade, the Dow Jones Industrial Average DJIA, -0.87% , the S&P 500 index SPX, -1.11% and the Nasdaq Composite Index COMP, -1.07% all finished lower after Trump's remarks. Trump's remarks followed reports that North Korea had successfully produced a nuclear warhead small enough to fit atop a missile.