The S&P 500 index flirted with a close below an important, long-term trend line as selling intensified late-Friday on the back of trade-war fears. The S&P 500 index SPX, -1.15% ended down 55.43 points, or 2.1%, at 2,588.26, barely above its 200-day MA at 2,585.38, according to FactSet data. Technical analysts pay attention to moving averages to help gauge bullish and bearish momentum in an asset. The equity index also closed below 2,600, considered a psychological round-number level that also could herald a bearish trend. The Dow Jones Industrial Average DJIA, -1.84% , meanwhile, finished the session down 424.69 points, or 1.8%, at 23,533.20, while the Nasdaq Composite Index COMP, -0.13% breached its 100-day moving average at 7,082.60 and closed off 2.4% at 6,992.67. The S&P 500 last closed below its 200-day MA on Feb. 9, a day after the Dow and S&P 500 fell into correction territory, defined as a drop of at least 10% from a recent high.