* Fed Chair Powell warns of economic woes and need for fiscal aid * Crude extends gains on supply pressures * Trump tweets he told Senate leader McConnell to stop negotiating stimulus bill * President Trump receiving top care for COVID-19 since release * Graphic: 2020 asset performance tmsnrt.rs/2yaDPgn * Graphic: World FX rates in 2020 tmsnrt.rs/2egbfVh (Updates with market moves after Trump calls off COVID stimulus talks) NEW YORK, Oct 6 (Reuters) - Wall Street promptly reversed solid gains late Tuesday, plunging into negative territory after President Donald Trump announced he was halting talks on coronavirus relief legislation until after the Nov. 3 elections. All three major U.S. stock indexes abruptly turned sharply lower on the news. Trump’s announcement comes on the heels of U.S. Federal Reserve Chair Jerome Powell warning of dire economic repercussions if Congress fails to pass additional fiscal stimulus. In remarks delivered online to the National Association for Business Economics, Powell warned the U.S. economy could slip into a downward spiral if the coronavirus is not contained and Congress fails to deliver additional fiscal support to businesses and households. “The things that are obvious to us are that small businesses are closing and unemployment remains high in the service sector,” said John Augustine, chief investment officer at Huntington National Bank in Columbus, Ohio. “The Fed aggressively wants to address both of those with more fiscal stimulus.” The Dow Jones Industrial Average fell 327.98 points, or 1.17%, to 27,820.66, the S&P 500 lost 39.32 points, or 1.15%, to 3,369.31 and the Nasdaq Composite dropped 145.03 points, or 1.28%, to 11,187.46. The pan-European STOXX 600 index was up 0.07% and MSCI’s gauge of stocks across the globe shed 0.60%. Crude prices extended gains, boosted by supply disruptions from approaching storms in the Gulf of Mexico and an ongoing oil worker strike in Norway. U.S. crude futures settled at $40.67 per barrel, a gain of 3.7%, while Brent gained 3.29% on the day to settle $42.65 per barrel. The dollar was essentially flat but gained ground after Trump’s announcement. The dollar index rose 0.13%, with the euro down 0.25% to $1.1751. The Japanese yen strengthened 0.16% versus the greenback at 105.59 per dollar, while Sterling was last trading at $1.2903, down 0.57% on the day. U.S. Treasury yields slightly extended their rise after Fed Chair Powell’s remarks. Benchmark 10-year notes last rose 7/32 in price to yield 0.7403%, from 0.762% late on Monday. The 30-year bond last rose 21/32 in price to yield 1.5387%, from 1.567% late on Monday. Gold prices were lower after the safe-haven precious metal erased earlier gains. Spot gold dropped 1.1% to $1,892.06 an ounce.