The energy sector was suffering a broad selloff, and was the leading loser of the S&P 500's 11 key sectors, weighed down by a revenue warning from NOV Inc. NOV, -10.34% and a drop in crude oil prices. The SPDR Energy Select Sector ETF XLE, -2.85% shed 2.3% in midday trading, with all 23 equity components losing ground, while the S&P 500 ticked up less than 0.1%. NOV's stock tumbled 9.3% to pace the declines, after the provider of equipment to the oil and gas industry said it now expects first-quarter revenue of between $1.20 billion and $1.25 billion, below the FactSet consensus of $1.32 billion, as severe weather in Texas and Oklahoma, and continued negative effects of the COVID-19 pandemic, led to softer-than-anticipated customer orders. Among other more-active energy ETF components, shares of Exxon Mobile Corp. XOM, -2.19% shed 1.8%, Marathon Oil Corp. MRO, -4.90% lost 3.9%, Occidental Petroleum Corp. OXY, -3.86% dropped 2.4%, Chevron Corp. CVX, -2.40% declined 2.0% and Kinder Morgan Inc. KMI, -2.51% gave up 1.9%. Meanwhile, crude oil futures CL00, -1.09% fell 1.2%, amid expectations that U.S. crude supplies rose for a fourth straight week.