US stocks tumbled after President Donald Trump said he is ending stimulus talks until after the election, just hours after Federal Reserve Chairman Jerome Powell renewed his warning that the economy will stumble without additional fiscal support.\r\nThe benchmark S&P 500 slumped as much as 1.5 percent after Trump tweeted his comments, erasing a gain of as much as 0.7 percent. Treasury yields surged and the dollar jumped against most its major peers.\r\n\r\n\r\n\u201cIt goes to show that the stimulus package was far from a forgone conclusion,\u201d said Matt Miskin, co-chief investment strategist at John Hancock Investment Management. \u201cThe market had had been pricing in better economic grown, cyclical were doing better, small caps were doing better.\r\nHouse Speaker Nancy Pelosi had called on Republicans to get on board with a version of the stimulus bill the House passed last week with only Democratic votes. But significant gaps remained between the Democrats\u2019 $2.2 trillion proposal and a $1.6 trillion offer backed by the White House.\r\nThere are also lingering concerns about the trajectory of the pandemic and its effect on the economy. New York City\u2019s seven-day average of daily cases is approaching Mayor Bill de Blasio\u2019s warning threshold of 550. In France, the country\u2019s statistics agency, downgraded its growth forecast to zero.\r\nElsewhere, the pound weakened after a report that the European Union has no plans to offer concessions to Boris Johnson before next week\u2019s Brexit deadline. Oil rose further after the biggest gain since May.