Among stocks, AveXis rose 77.6 percent after Swiss drugmaker Novartis offered to buy the gene therapy company for $8.7 billion. In individual stocks, Facebook remained in focus as the company's CEO Mark Zuckerberg testified on Capitol Hill for second day. The Nasdaq composite climbed 71 points, or 1 percent, to 7,140.
The rising tensions sent oil prices surging, boosting energy stocks.SPNY 1 percent.
Stocks are clawing back much of the ground they lost in an early tumble and are trading mixed at midday on Wall Street.
U.S. stocks tumbled Wednesday as President Donald Trump escalated tensions with Russian Federation through a series of tweets, rattling investor nerves at a time when fears of a global trade war were starting to ebb.
Bond prices fell. The yield on the 10-year Treasury note rose to 2.78 percent.
The S&P 500 rose 21 points, or 0.8 percent, to 2,663.
The Dow average increased 46 points, or 0.2 percent, to 23,979.
The week also marks the start of earnings season with big USA banks such as JPMorgan Chase, Citigroup and Wells Fargo set to report first-quarter results on Friday.
The major Wall Street indexes edged even lower after minutes from the Federal Open Market Committee showed concern among a few of its members that rising inflation might require a faster pace of interest rate hikes than anticipated.
The early losses marked a reversal of two days of gains driven largely by reduced fears around a global trade war. JPMorgan Chase added 2.4 percent. The market had rallied the day before on signs that trade tensions between the US and China were easing.
Equity futures extended losses just before 7 a.m. ET as Trump tweeted for Russia to "Get ready" because missiles would "be coming, nice and new and 'smart!'" Trump has been weighing whether to strike Syria over a suspected chemical weapons attack of a rebel-held town Saturday that left dozens of people dead and that the United States and local aid groups have blamed on the Russian-backed Syrian government.
The Dow Jones industrial average increased 345 points, or 1.4 percent, to 24,279. While the U.K.'s FTSE 100 Index edged down by 0.1 percent, the French CAC 40 Index dropped by 0.6 percent and the German DAX Index slid by 0.8 percent. The Nasdaq composite added 135 points, or 2 percent, to 7,050.