Billionaire Elon Musk’s purchase of a major stake in Twitter added impetus to early trading on Wall Street on Monday, where stocks mostly rose.

News the Tesla founder bought nearly 73.5 million shares worth about $2.9 billion and equal to a 9.2 percent stake in the social media company he has frequently sparred with sent Twitter shares rising 21 percent shortly after the open.

While the stake is relatively small, and the company itself isn’t weighty enough to move the market on its own, the news has undergirded the Dow and Nasdaq’s upward move, analysts said.

“What the market is really responding to is the timing of Musk’s purchase and the supposition that it is an encouraging signal that longer-term investment opportunities might be availing themselves now in former high-flying stocks,” said Briefing.com analyst Patrick J. O’Hare.

But the prospect of rising interest rates meant to rein in inflation, and the danger that could tip the worlds’ largest economy into a recession, continues to loom over markets, which are already fretting over the impact of Russia’s invasion of Ukraine.

About 20 minutes into the first trading session of the week, the tech-rich Nasdaq Composite Index had gained 1.0 percent to 14,402.52, and the broad-based S&P 500 was up 0.1 percent at 4,552.27.

The benchmark Dow Jones Industrial Average was down 0.3 percent at 34,705.44.